CWE-611
AllowedImproper Restriction of XML External Entity Reference
Abstraction: Base · Status: Draft
The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.
1831 vulnerabilities reference this CWE, most recent first.
GHSA-H2VQ-7GF2-QW9V
Vulnerability from github – Published: 2022-05-17 00:30 – Updated: 2023-10-23 17:24XML external entity (XXE) vulnerability in Umbraco CMS before 7.7.3 allows attackers to obtain sensitive information by reading files on the server or sending TCP requests to intranet hosts (aka SSRF), related to Umbraco.Web/umbraco.presentation/umbraco/dialogs/importDocumenttype.aspx.cs.
{
"affected": [
{
"package": {
"ecosystem": "NuGet",
"name": "UmbracoCms.Web"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "7.7.3"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2017-15280"
],
"database_specific": {
"cwe_ids": [
"CWE-611"
],
"github_reviewed": true,
"github_reviewed_at": "2023-07-26T23:13:52Z",
"nvd_published_at": "2017-10-12T08:29:00Z",
"severity": "MODERATE"
},
"details": "XML external entity (XXE) vulnerability in Umbraco CMS before 7.7.3 allows attackers to obtain sensitive information by reading files on the server or sending TCP requests to intranet hosts (aka SSRF), related to `Umbraco.Web/umbraco.presentation/umbraco/dialogs/importDocumenttype.aspx.cs`.",
"id": "GHSA-h2vq-7gf2-qw9v",
"modified": "2023-10-23T17:24:47Z",
"published": "2022-05-17T00:30:20Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2017-15280"
},
{
"type": "WEB",
"url": "https://github.com/umbraco/Umbraco-CMS/commit/5dde2efe0d2b3a47d17439e03acabb7ea2befb64"
},
{
"type": "PACKAGE",
"url": "https://github.com/umbraco/Umbraco-CMS"
},
{
"type": "WEB",
"url": "https://github.com/umbraco/Umbraco-CMS/blob/release-7.7.3/src/Umbraco.Web/Umbraco.Web.csproj"
},
{
"type": "WEB",
"url": "http://issues.umbraco.org/issue/U4-10506"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
],
"summary": "Umbraco CMS XXE Vulnerability"
}
GHSA-H384-PH77-3699
Vulnerability from github – Published: 2023-03-21 18:30 – Updated: 2023-03-24 22:19A vulnerability was found in zwczou WeChat SDK Python 0.3.0 and classified as critical. This issue affects the function validate/to_xml. The manipulation leads to xml external entity reference. The attack may be initiated remotely. Upgrading to version 0.5.5 is able to address this issue. The name of the patch is e54abadc777715b6dcb545c13214d1dea63df6c9. It is recommended to upgrade the affected component. The associated identifier of this vulnerability is VDB-223403.
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "weixin-python"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.5.5"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2018-25082"
],
"database_specific": {
"cwe_ids": [
"CWE-611"
],
"github_reviewed": true,
"github_reviewed_at": "2023-03-21T22:41:46Z",
"nvd_published_at": "2023-03-21T18:15:00Z",
"severity": "CRITICAL"
},
"details": "A vulnerability was found in zwczou WeChat SDK Python 0.3.0 and classified as critical. This issue affects the function validate/to_xml. The manipulation leads to xml external entity reference. The attack may be initiated remotely. Upgrading to version 0.5.5 is able to address this issue. The name of the patch is e54abadc777715b6dcb545c13214d1dea63df6c9. It is recommended to upgrade the affected component. The associated identifier of this vulnerability is VDB-223403.",
"id": "GHSA-h384-ph77-3699",
"modified": "2023-03-24T22:19:53Z",
"published": "2023-03-21T18:30:19Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2018-25082"
},
{
"type": "WEB",
"url": "https://github.com/zwczou/weixin-python/pull/30"
},
{
"type": "WEB",
"url": "https://github.com/zwczou/weixin-python/commit/e54abadc777715b6dcb545c13214d1dea63df6c9"
},
{
"type": "PACKAGE",
"url": "https://github.com/zwczou/weixin-python"
},
{
"type": "WEB",
"url": "https://github.com/zwczou/weixin-python/releases/tag/v0.5.5"
},
{
"type": "WEB",
"url": "https://vuldb.com/?ctiid.223403"
},
{
"type": "WEB",
"url": "https://vuldb.com/?id.223403"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
],
"summary": "weixin-python XML External Entity vulnerability"
}
GHSA-H39X-GXCQ-JM2V
Vulnerability from github – Published: 2026-07-29 21:31 – Updated: 2026-07-30 21:31Jinher OA C6 contains an XML External Entity (XXE) injection vulnerability in the /c6/JHSoft.Web.HrmAttendance/sp_manager_getUserlist.aspx/GetXmlHttp endpoint. An unauthenticated remote attacker can send a crafted XML payload to read arbitrary files from the server via an out-of-band attack.
{
"affected": [],
"aliases": [
"CVE-2026-50782"
],
"database_specific": {
"cwe_ids": [
"CWE-611"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-07-29T21:17:47Z",
"severity": "HIGH"
},
"details": "Jinher OA C6 contains an XML External Entity (XXE) injection vulnerability in the /c6/JHSoft.Web.HrmAttendance/sp_manager_getUserlist.aspx/GetXmlHttp endpoint. An unauthenticated remote attacker can send a crafted XML payload to read arbitrary files from the server via an out-of-band attack.",
"id": "GHSA-h39x-gxcq-jm2v",
"modified": "2026-07-30T21:31:31Z",
"published": "2026-07-29T21:31:01Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50782"
},
{
"type": "WEB",
"url": "https://github.com/dihe123/CNVD-Jinher-OA-XXE/blob/main/README.md"
},
{
"type": "WEB",
"url": "https://github.com/dihe123/CNVD-Jinher-OA-XXE/tree/main"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-H455-6C5F-P957
Vulnerability from github – Published: 2022-05-24 16:54 – Updated: 2022-12-03 00:30IBM InfoSphere Global Name Management 5.0 and 6.0 and IBM InfoSphere Identity Insight 8.1 and 9.0 is vulnerable to an XML External Entity Injection (XXE) attack when processing XML data. A remote attacker could exploit this vulnerability to expose sensitive information or consume memory resources. IBM X-Force ID: 162890.
{
"affected": [],
"aliases": [
"CVE-2019-4433"
],
"database_specific": {
"cwe_ids": [
"CWE-611"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2019-08-20T19:15:00Z",
"severity": "HIGH"
},
"details": "IBM InfoSphere Global Name Management 5.0 and 6.0 and IBM InfoSphere Identity Insight 8.1 and 9.0 is vulnerable to an XML External Entity Injection (XXE) attack when processing XML data. A remote attacker could exploit this vulnerability to expose sensitive information or consume memory resources. IBM X-Force ID: 162890.",
"id": "GHSA-h455-6c5f-p957",
"modified": "2022-12-03T00:30:19Z",
"published": "2022-05-24T16:54:09Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2019-4433"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/162890"
},
{
"type": "WEB",
"url": "https://www.ibm.com/support/docview.wss?uid=ibm10958079"
},
{
"type": "WEB",
"url": "https://www.ibm.com/support/docview.wss?uid=ibm10958081"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:L",
"type": "CVSS_V3"
}
]
}
GHSA-H4WX-78P9-FWXW
Vulnerability from github – Published: 2022-11-16 12:00 – Updated: 2025-04-30 20:27SourceMonitor Plugin 0.2 and earlier does not configure its XML parser to prevent XML external entity (XXE) attacks.
This allows attackers able to control XML input files for the 'Publish SourceMonitor results' post-build step to have agent processes parse a crafted file that uses external entities for extraction of secrets from the Jenkins agent or server-side request forgery.
Because Jenkins agent processes usually execute build tools whose input (source code, build scripts, etc.) is controlled externally, this vulnerability only has a real impact in very narrow circumstances: when attackers can control XML files, but are unable to change build steps, Jenkinsfiles, test code that gets executed on the agents, or similar.
{
"affected": [
{
"package": {
"ecosystem": "Maven",
"name": "com.thalesgroup.hudson.plugins:sourcemonitor"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "0.2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2022-45396"
],
"database_specific": {
"cwe_ids": [
"CWE-611"
],
"github_reviewed": true,
"github_reviewed_at": "2022-11-21T22:24:17Z",
"nvd_published_at": "2022-11-15T20:15:00Z",
"severity": "MODERATE"
},
"details": "SourceMonitor Plugin 0.2 and earlier does not configure its XML parser to prevent XML external entity (XXE) attacks.\n\nThis allows attackers able to control XML input files for the \u0027Publish SourceMonitor results\u0027 post-build step to have agent processes parse a crafted file that uses external entities for extraction of secrets from the Jenkins agent or server-side request forgery.\n\nBecause Jenkins agent processes usually execute build tools whose input (source code, build scripts, etc.) is controlled externally, this vulnerability only has a real impact in very narrow circumstances: when attackers can control XML files, but are unable to change build steps, Jenkinsfiles, test code that gets executed on the agents, or similar.",
"id": "GHSA-h4wx-78p9-fwxw",
"modified": "2025-04-30T20:27:35Z",
"published": "2022-11-16T12:00:23Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-45396"
},
{
"type": "PACKAGE",
"url": "https://github.com/jenkinsci/sourcemonitor-plugin"
},
{
"type": "WEB",
"url": "https://www.jenkins.io/security/advisory/2022-11-15/#SECURITY-2927"
},
{
"type": "WEB",
"url": "http://www.openwall.com/lists/oss-security/2022/11/15/4"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N",
"type": "CVSS_V3"
}
],
"summary": "XXE vulnerability on agents in Jenkins SourceMonitor Plugin"
}
GHSA-H57P-MM7W-9RCX
Vulnerability from github – Published: 2022-05-14 01:56 – Updated: 2022-05-14 01:56An XXE vulnerability in the OPC UA Java and .NET Legacy Stack can allow remote attackers to trigger a denial of service.
{
"affected": [],
"aliases": [
"CVE-2018-12585"
],
"database_specific": {
"cwe_ids": [
"CWE-611"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2018-09-14T21:29:00Z",
"severity": "HIGH"
},
"details": "An XXE vulnerability in the OPC UA Java and .NET Legacy Stack can allow remote attackers to trigger a denial of service.",
"id": "GHSA-h57p-mm7w-9rcx",
"modified": "2022-05-14T01:56:13Z",
"published": "2022-05-14T01:56:13Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2018-12585"
},
{
"type": "WEB",
"url": "https://opcfoundation-onlineapplications.org/faq/SecurityBulletins/OPC_Foundation_Security_Bulletin_CVE-2018-12585.pdf"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/105538"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-H67G-969J-MGR3
Vulnerability from github – Published: 2022-05-24 16:48 – Updated: 2024-04-04 01:02BlogEngine.NET 3.3.7 and earlier allows XXE via an apml file to syndication.axd.
{
"affected": [],
"aliases": [
"CVE-2019-11392"
],
"database_specific": {
"cwe_ids": [
"CWE-611"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2019-06-21T19:15:00Z",
"severity": "HIGH"
},
"details": "BlogEngine.NET 3.3.7 and earlier allows XXE via an apml file to syndication.axd.",
"id": "GHSA-h67g-969j-mgr3",
"modified": "2024-04-04T01:02:36Z",
"published": "2022-05-24T16:48:35Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2019-11392"
},
{
"type": "WEB",
"url": "https://www.securitymetrics.com/blog/blogenginenet-xml-external-entity-attacks"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-H755-H99P-9FFV
Vulnerability from github – Published: 2022-05-14 01:40 – Updated: 2024-01-08 20:11An issue was discovered in weixin-java-tools. There is an XXE vulnerability in the getXmlDoc method of the BaseWxPayResult.java file. NOTE: this issue exists because of an incomplete fix for CVE-2018-20318.
{
"affected": [
{
"package": {
"ecosystem": "Maven",
"name": "com.github.binarywang:weixin-java-common"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "3.3.2.B"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2019-5312"
],
"database_specific": {
"cwe_ids": [
"CWE-611"
],
"github_reviewed": true,
"github_reviewed_at": "2024-01-08T20:11:00Z",
"nvd_published_at": "2019-01-04T16:29:00Z",
"severity": "CRITICAL"
},
"details": "An issue was discovered in weixin-java-tools. There is an XXE vulnerability in the getXmlDoc method of the BaseWxPayResult.java file. NOTE: this issue exists because of an incomplete fix for CVE-2018-20318.",
"id": "GHSA-h755-h99p-9ffv",
"modified": "2024-01-08T20:11:00Z",
"published": "2022-05-14T01:40:24Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2019-5312"
},
{
"type": "WEB",
"url": "https://github.com/Wechat-Group/WxJava/issues/903"
},
{
"type": "WEB",
"url": "https://github.com/Wechat-Group/WxJava/issues/903#issuecomment-453747039"
},
{
"type": "WEB",
"url": "https://github.com/Wechat-Group/WxJava/commit/8ec61d1328f50e23cd14285a950ca57a088b32b2"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
],
"summary": "XML External Entity Reference in weixin-java-tools"
}
GHSA-H7PC-9M8F-584G
Vulnerability from github – Published: 2021-12-09 00:01 – Updated: 2021-12-14 00:01National Library of the Netherlands multiNER <= c0440948057afc6e3d6b4903a7c05e666b94a3bc is affected by an XML External Entity (XXE) vulnerability in multiNER/ner.py. Since XML parsing resolves external entities, a malicious XML stream could leak internal files and/or cause a DoS.
{
"affected": [],
"aliases": [
"CVE-2021-44557"
],
"database_specific": {
"cwe_ids": [
"CWE-611"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2021-12-08T12:15:00Z",
"severity": "CRITICAL"
},
"details": "National Library of the Netherlands multiNER \u003c= c0440948057afc6e3d6b4903a7c05e666b94a3bc is affected by an XML External Entity (XXE) vulnerability in multiNER/ner.py. Since XML parsing resolves external entities, a malicious XML stream could leak internal files and/or cause a DoS.",
"id": "GHSA-h7pc-9m8f-584g",
"modified": "2021-12-14T00:01:39Z",
"published": "2021-12-09T00:01:03Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2021-44557"
},
{
"type": "WEB",
"url": "https://github.com/KBNLresearch/multiNER/pull/3"
},
{
"type": "WEB",
"url": "https://github.com/KBNLresearch/multiNER"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-H7QF-QMF3-85QG
Vulnerability from github – Published: 2025-06-25 14:14 – Updated: 2025-06-25 14:14Summary
A critical XML External Entity (XXE) vulnerability exists in the xunit-xml-plugin used by Allure 2. The plugin fails to securely configure the XML parser (DocumentBuilderFactory) and allows external entity expansion when processing test result .xml files. This allows attackers to read arbitrary files from the file system and potentially trigger server-side request forgery (SSRF).
Details
In \allure2-main\plugins\xunit-xml-plugin\src\main\java\io\qameta\allure\xunitxml\XunitXmlPlugin.java the application uses DocumentBuilderFactory without disabling DTDs or external entities. By generating a report with a malicious xml file within it, an attacker can perform XXE to leverage SSRF, or to read system files.
PoC
To recreate this vulnerability, you need to install allure for command-line (In my POC I used a Windows 11 Machine).
- Create a folder called
allure, and within it, create a malicious XML file. I will attach my SSRF and file reading payloads, however, for the rest of the POC, I will focus on reading system files for better screenshots.
SSRF (replace webhook link with your own)
Reading System Files
- Put the malicious .xml file into the
alluredirectory created previously - Run the following command to run the report
allure generate C:\path\to\directory\allure -o report --clean - To view and confirm the executed payload, run
allure open report - When the report opens, confirm the payload executedby going to
Categories > Product defects > <payload response>
Impact
The explained XXE vulnerability can lead to Arbitrary File Disclosure and Server-Side Request Forgery. This exploitation can also be carried out silently, meaning it can be carried out without user interaction if the tool is automated within an application, and can go undetected with a carefully crafted payload. This could allow a malicious actor to view other source codes which may contain API or product keys, internal application URLs, or other secret items. This makes it an especially high risk when ran within a CI/CD platform.
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 2.34.0"
},
"package": {
"ecosystem": "Maven",
"name": "io.qameta.allure.plugins:xunit-xml-plugin"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.34.1"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 2.34.0"
},
"package": {
"ecosystem": "Maven",
"name": "io.qameta.allure.plugins:junit-xml-plugin"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.34.1"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 2.34.0"
},
"package": {
"ecosystem": "Maven",
"name": "io.qameta.allure.plugins:trx-plugin"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.34.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2025-52888"
],
"database_specific": {
"cwe_ids": [
"CWE-611"
],
"github_reviewed": true,
"github_reviewed_at": "2025-06-25T14:14:09Z",
"nvd_published_at": "2025-06-24T20:15:26Z",
"severity": "HIGH"
},
"details": "### Summary\nA critical XML External Entity (XXE) vulnerability exists in the xunit-xml-plugin used by Allure 2. The plugin fails to securely configure the XML parser (`DocumentBuilderFactory`) and allows external entity expansion when processing test result .xml files. This allows attackers to read arbitrary files from the file system and potentially trigger server-side request forgery (SSRF).\n\n### Details\nIn `\\allure2-main\\plugins\\xunit-xml-plugin\\src\\main\\java\\io\\qameta\\allure\\xunitxml\\XunitXmlPlugin.java` the application uses `DocumentBuilderFactory` without disabling DTDs or external entities. By generating a report with a malicious xml file within it, an attacker can perform XXE to leverage SSRF, or to read system files.\n\n### PoC\nTo recreate this vulnerability, you need to install allure for command-line (In my POC I used a Windows 11 Machine). \n\n1. Create a folder called `allure`, and within it, create a malicious XML file. I will attach my SSRF and file reading payloads, however, for the rest of the POC, I will focus on reading system files for better screenshots.\n##SSRF (replace webhook link with your own)\n\n\n##Reading System Files\n\n\n2. Put the malicious .xml file into the `allure` directory created previously\n3. Run the following command to run the report `allure generate C:\\path\\to\\directory\\allure -o report --clean`\n4. To view and confirm the executed payload, run `allure open report`\n5. When the report opens, confirm the payload executedby going to `Categories \u003e Product defects \u003e \u003cpayload response\u003e`\n\n\n\n\n### Impact\nThe explained XXE vulnerability can lead to Arbitrary File Disclosure and Server-Side Request Forgery. This exploitation can also be carried out silently, meaning it can be carried out without user interaction if the tool is automated within an application, and can go undetected with a carefully crafted payload. This could allow a malicious actor to view other source codes which may contain API or product keys, internal application URLs, or other secret items. This makes it an especially high risk when ran within a CI/CD platform.",
"id": "GHSA-h7qf-qmf3-85qg",
"modified": "2025-06-25T14:14:09Z",
"published": "2025-06-25T14:14:09Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/allure-framework/allure2/security/advisories/GHSA-h7qf-qmf3-85qg"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-52888"
},
{
"type": "WEB",
"url": "https://github.com/allure-framework/allure2/commit/cbcb33719851ff70adce85d38e15d20fc58d4eb7"
},
{
"type": "PACKAGE",
"url": "https://github.com/allure-framework/allure2"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
],
"summary": "Allure Report allows Improper XXE Restriction via DocumentBuilderFactory"
}
Mitigation
Many XML parsers and validators can be configured to disable external entity expansion.
CAPEC-221: Data Serialization External Entities Blowup
This attack takes advantage of the entity replacement property of certain data serialization languages (e.g., XML, YAML, etc.) where the value of the replacement is a URI. A well-crafted file could have the entity refer to a URI that consumes a large amount of resources to create a denial of service condition. This can cause the system to either freeze, crash, or execute arbitrary code depending on the URI.