CWE-400
DiscouragedUncontrolled Resource Consumption
Abstraction: Class · Status: Draft
The product does not properly control the allocation and maintenance of a limited resource.
6465 vulnerabilities reference this CWE, most recent first.
GHSA-WJJ9-47HV-QCQF
Vulnerability from github – Published: 2026-09-15 21:31 – Updated: 2026-09-15 21:31A vulnerability exists in the underlying operating system of HPE Networking EdgeConnect SD-WAN Gateways. Successful exploitation could allow an unauthenticated remote attacker to conduct a denial-of-service attack on the affected service.
{
"affected": [],
"aliases": [
"CVE-2026-76686"
],
"database_specific": {
"cwe_ids": [
"CWE-400"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-15T20:17:50Z",
"severity": "HIGH"
},
"details": "A vulnerability exists in the underlying operating system of HPE Networking EdgeConnect SD-WAN Gateways. Successful exploitation could allow an unauthenticated remote attacker to conduct a denial-of-service attack on the affected service.",
"id": "GHSA-wjj9-47hv-qcqf",
"modified": "2026-09-15T21:31:35Z",
"published": "2026-09-15T21:31:35Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-76686"
},
{
"type": "WEB",
"url": "https://support.hpe.com/hpesc/public/docDisplay?docId=hpesbnw05135en_us\u0026docLocale=en_US"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-WJJC-M3FC-FCM8
Vulnerability from github – Published: 2022-05-17 05:52 – Updated: 2024-11-26 18:40The password_checker function in config/multiconfig.py in MoinMoin prior to version 1.6.1 uses the cracklib and python-crack features even though they are not thread-safe, which allows remote attackers to cause a denial of service (segmentation fault and crash) via unknown vectors.
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "moin"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.6.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2008-6549"
],
"database_specific": {
"cwe_ids": [
"CWE-400"
],
"github_reviewed": true,
"github_reviewed_at": "2024-02-09T19:33:55Z",
"nvd_published_at": "2009-03-30T01:30:00Z",
"severity": "HIGH"
},
"details": "The password_checker function in `config/multiconfig.py` in MoinMoin prior to version 1.6.1 uses the cracklib and python-crack features even though they are not thread-safe, which allows remote attackers to cause a denial of service (segmentation fault and crash) via unknown vectors.",
"id": "GHSA-wjjc-m3fc-fcm8",
"modified": "2024-11-26T18:40:12Z",
"published": "2022-05-17T05:52:47Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2008-6549"
},
{
"type": "PACKAGE",
"url": "https://github.com/moinwiki/moin"
},
{
"type": "WEB",
"url": "https://github.com/pypa/advisory-database/tree/main/vulns/moin/PYSEC-2009-12.yaml"
},
{
"type": "WEB",
"url": "https://web.archive.org/web/20080410051007/http://moinmo.in/SecurityFixes"
},
{
"type": "WEB",
"url": "https://web.archive.org/web/20211206185024/http://hg.moinmo.in/moin/1.6/rev/35ff7a9b1546"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "MoinMoin Denial of Service vulnerability via password_checker function"
}
GHSA-WJJX-5Q7V-M436
Vulnerability from github – Published: 2026-06-17 18:35 – Updated: 2026-06-17 18:35Vulnerability in the Oracle Enterprise Manager Base Platform product of Oracle Enterprise Manager (component: Agent Next Gen). Supported versions that are affected are 13.5 and 24.1. Easily exploitable vulnerability allows unauthenticated attacker with network access via HTTPS to compromise Oracle Enterprise Manager Base Platform. Successful attacks of this vulnerability can result in unauthorized ability to cause a hang or frequently repeatable crash (complete DOS) of Oracle Enterprise Manager Base Platform as well as unauthorized update, insert or delete access to some of Oracle Enterprise Manager Base Platform accessible data. CVSS 3.1 Base Score 8.2 (Integrity and Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H).
{
"affected": [],
"aliases": [
"CVE-2026-46866"
],
"database_specific": {
"cwe_ids": [
"CWE-400"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-06-17T10:54:04Z",
"severity": "HIGH"
},
"details": "Vulnerability in the Oracle Enterprise Manager Base Platform product of Oracle Enterprise Manager (component: Agent Next Gen). Supported versions that are affected are 13.5 and 24.1. Easily exploitable vulnerability allows unauthenticated attacker with network access via HTTPS to compromise Oracle Enterprise Manager Base Platform. Successful attacks of this vulnerability can result in unauthorized ability to cause a hang or frequently repeatable crash (complete DOS) of Oracle Enterprise Manager Base Platform as well as unauthorized update, insert or delete access to some of Oracle Enterprise Manager Base Platform accessible data. CVSS 3.1 Base Score 8.2 (Integrity and Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H).",
"id": "GHSA-wjjx-5q7v-m436",
"modified": "2026-06-17T18:35:33Z",
"published": "2026-06-17T18:35:33Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-46866"
},
{
"type": "WEB",
"url": "https://www.oracle.com/security-alerts/cspujun2026.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-WJM3-FQ3R-5X46
Vulnerability from github – Published: 2021-05-18 21:07 – Updated: 2024-05-20 21:31GJSON <1.6.5 allows attackers to cause a denial of service (remote) via crafted JSON.
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/tidwall/gjson"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.6.5"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2020-36066"
],
"database_specific": {
"cwe_ids": [
"CWE-400"
],
"github_reviewed": true,
"github_reviewed_at": "2021-05-18T21:00:38Z",
"nvd_published_at": null,
"severity": "HIGH"
},
"details": "GJSON \u003c1.6.5 allows attackers to cause a denial of service (remote) via crafted JSON.",
"id": "GHSA-wjm3-fq3r-5x46",
"modified": "2024-05-20T21:31:34Z",
"published": "2021-05-18T21:07:54Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2020-36066"
},
{
"type": "WEB",
"url": "https://github.com/tidwall/gjson/issues/195"
},
{
"type": "WEB",
"url": "https://github.com/tidwall/gjson/issues/195#issuecomment-755303148"
},
{
"type": "WEB",
"url": "https://github.com/tidwall/gjson/commit/9f58baa7a613f89dfdc764c39e47fd3a15606153"
},
{
"type": "WEB",
"url": "https://github.com/tidwall/match/commit/c2f534168b739a7ec1821a33839fb2f029f26bbc"
},
{
"type": "PACKAGE",
"url": "https://github.com/tidwall/gjson"
},
{
"type": "WEB",
"url": "https://pkg.go.dev/vuln/GO-2022-0957"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
],
"summary": "github.com/tidwall/gjson is vulnerable to Denial of service"
}
GHSA-WJMF-P669-5M5P
Vulnerability from github – Published: 2026-08-28 18:43 – Updated: 2026-08-28 18:43Problem description
Protego constructs regular expressions to match URLs against robots.txt Allow: and Disallow: directives, see protego._urlpattern._URLPattern._prepare_pattern_for_regex(). Every * in the directive value is translated into a lazy .*? regex piece, thus a specially crafted directive value with many asterisks may produce a regex that freezes the parser due to exponential backtracking.
Impact
Parsing a specially crafted robots.txt with protego.Protego.parse() and then trying to match an URL with protego.Protego.can_fetch() results in the latter call not returning for a period dependent on the length of the URL.
Proof of concept
from protego import Protego
robotstxt = f"""
User-agent: *
Disallow: /{"*1" * 12}*Z
"""
rp = Protego.parse(robotstxt)
url = "/" + "1" * 60
rp.can_fetch(url, "mybot") # freezes
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 0.6.1"
},
"package": {
"ecosystem": "PyPI",
"name": "Protego"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.6.2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-55520"
],
"database_specific": {
"cwe_ids": [
"CWE-1333",
"CWE-400"
],
"github_reviewed": true,
"github_reviewed_at": "2026-08-28T18:43:02Z",
"nvd_published_at": null,
"severity": "HIGH"
},
"details": "### Problem description\n\nProtego constructs regular expressions to match URLs against `robots.txt` `Allow:` and `Disallow:` directives, see `protego._urlpattern._URLPattern._prepare_pattern_for_regex()`. Every `*` in the directive value is translated into a lazy `.*?` regex piece, thus a specially crafted directive value with many asterisks may produce a regex that freezes the parser due to exponential backtracking.\n\n### Impact\n\nParsing a specially crafted `robots.txt` with `protego.Protego.parse()` and then trying to match an URL with `protego.Protego.can_fetch()` results in the latter call not returning for a period dependent on the length of the URL.\n\n### Proof of concept\n\n```python\nfrom protego import Protego\n\nrobotstxt = f\"\"\"\nUser-agent: *\nDisallow: /{\"*1\" * 12}*Z\n\"\"\"\nrp = Protego.parse(robotstxt)\nurl = \"/\" + \"1\" * 60\nrp.can_fetch(url, \"mybot\") # freezes\n```",
"id": "GHSA-wjmf-p669-5m5p",
"modified": "2026-08-28T18:43:02Z",
"published": "2026-08-28T18:43:02Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/scrapy/protego/security/advisories/GHSA-wjmf-p669-5m5p"
},
{
"type": "WEB",
"url": "https://github.com/scrapy/protego/commit/785940181659bf440ba82f1da148fade5087e858"
},
{
"type": "PACKAGE",
"url": "https://github.com/scrapy/protego"
},
{
"type": "WEB",
"url": "https://github.com/scrapy/protego/releases/tag/0.6.2"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Protego has exponential backtracking ReDoS in robots.txt URL wildcard matching"
}
GHSA-WJPF-6J9Q-4H5X
Vulnerability from github – Published: 2022-05-24 17:22 – Updated: 2022-05-24 17:22TCP/IP function included in the firmware of Mitsubishi Electric GOT2000 series (CoreOS with version -Y and earlier installed in GT27 Model, GT25 Model, and GT23 Model) contains a resource management error vulnerability, which may allow a remote attacker to stop the network functions of the products or execute a malicious program via a specially crafted packet.
{
"affected": [],
"aliases": [
"CVE-2020-5600"
],
"database_specific": {
"cwe_ids": [
"CWE-400"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2020-07-07T09:15:00Z",
"severity": "MODERATE"
},
"details": "TCP/IP function included in the firmware of Mitsubishi Electric GOT2000 series (CoreOS with version -Y and earlier installed in GT27 Model, GT25 Model, and GT23 Model) contains a resource management error vulnerability, which may allow a remote attacker to stop the network functions of the products or execute a malicious program via a specially crafted packet.",
"id": "GHSA-wjpf-6j9q-4h5x",
"modified": "2022-05-24T17:22:34Z",
"published": "2022-05-24T17:22:34Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2020-5600"
},
{
"type": "WEB",
"url": "https://jvn.jp/en/vu/JVNVU95413676/index.html"
},
{
"type": "WEB",
"url": "https://www.mitsubishielectric.com/en/psirt/vulnerability/pdf/2020-005_en.pdf"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-WJPV-64V2-2QPQ
Vulnerability from github – Published: 2025-03-20 12:32 – Updated: 2025-03-20 19:13In h2oai/h2o-3 version 3.46.0.1, the run_tool command exposes classes in the water.tools package through the ast parser. This includes the XGBoostLibExtractTool class, which can be exploited to shut down the server and write large files to arbitrary directories, leading to a denial of service.
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "h2o"
},
"ranges": [
{
"events": [
{
"introduced": "3.34.0.1"
},
{
"last_affected": "3.46.0.1"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Maven",
"name": "ai.h2o:h2o-ext-xgboost"
},
"ranges": [
{
"events": [
{
"introduced": "3.34.0.1"
},
{
"last_affected": "3.46.0.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2024-10572"
],
"database_specific": {
"cwe_ids": [
"CWE-400",
"CWE-94"
],
"github_reviewed": true,
"github_reviewed_at": "2025-03-20T19:13:16Z",
"nvd_published_at": "2025-03-20T10:15:17Z",
"severity": "HIGH"
},
"details": "In h2oai/h2o-3 version 3.46.0.1, the `run_tool` command exposes classes in the `water.tools` package through the `ast` parser. This includes the `XGBoostLibExtractTool` class, which can be exploited to shut down the server and write large files to arbitrary directories, leading to a denial of service.",
"id": "GHSA-wjpv-64v2-2qpq",
"modified": "2025-03-20T19:13:16Z",
"published": "2025-03-20T12:32:39Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-10572"
},
{
"type": "PACKAGE",
"url": "https://github.com/h2oai/h2o-3"
},
{
"type": "WEB",
"url": "https://github.com/h2oai/h2o-3/blob/5e45e780f597961bda73adff765976db975f204b/h2o-extensions/xgboost/src/main/java/water/tools/XGBoostLibExtractTool.java#L12"
},
{
"type": "WEB",
"url": "https://huntr.com/bounties/db8939a0-9be8-4d0f-a8b0-1bd181666da2"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
],
"summary": "H2O Vulnerable to Denial of Service (DoS) and File Write"
}
GHSA-WJQH-4VFG-J2PJ
Vulnerability from github – Published: 2024-10-08 18:33 – Updated: 2024-10-08 18:33Windows Online Certificate Status Protocol (OCSP) Server Denial of Service Vulnerability
{
"affected": [],
"aliases": [
"CVE-2024-43545"
],
"database_specific": {
"cwe_ids": [
"CWE-400"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-10-08T18:15:19Z",
"severity": "HIGH"
},
"details": "Windows Online Certificate Status Protocol (OCSP) Server Denial of Service Vulnerability",
"id": "GHSA-wjqh-4vfg-j2pj",
"modified": "2024-10-08T18:33:16Z",
"published": "2024-10-08T18:33:16Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-43545"
},
{
"type": "WEB",
"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2024-43545"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-WJRC-F8QW-J9Q6
Vulnerability from github – Published: 2022-05-14 00:55 – Updated: 2022-05-14 00:55In LibSass prior to 3.5.5, functions inside ast.cpp for IMPLEMENT_AST_OPERATORS expansion allow attackers to cause a denial-of-service resulting from stack consumption via a crafted sass file, as demonstrated by recursive calls involving clone(), cloneChildren(), and copy().
{
"affected": [],
"aliases": [
"CVE-2018-19838"
],
"database_specific": {
"cwe_ids": [
"CWE-400"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2018-12-04T09:29:00Z",
"severity": "MODERATE"
},
"details": "In LibSass prior to 3.5.5, functions inside ast.cpp for IMPLEMENT_AST_OPERATORS expansion allow attackers to cause a denial-of-service resulting from stack consumption via a crafted sass file, as demonstrated by recursive calls involving clone(), cloneChildren(), and copy().",
"id": "GHSA-wjrc-f8qw-j9q6",
"modified": "2022-05-14T00:55:57Z",
"published": "2022-05-14T00:55:57Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2018-19838"
},
{
"type": "WEB",
"url": "https://github.com/sass/libsass/issues/2660"
},
{
"type": "WEB",
"url": "http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00047.html"
},
{
"type": "WEB",
"url": "http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00051.html"
},
{
"type": "WEB",
"url": "http://lists.opensuse.org/opensuse-security-announce/2019-08/msg00027.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-WJXG-4572-7WFG
Vulnerability from github – Published: 2025-07-15 21:31 – Updated: 2025-07-15 21:31Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are 8.0.0-8.0.42, 8.4.0-8.4.5 and 9.0.0-9.3.0. Easily exploitable vulnerability allows high privileged attacker with network access via multiple protocols to compromise MySQL Server. Successful attacks of this vulnerability can result in unauthorized ability to cause a hang or frequently repeatable crash (complete DOS) of MySQL Server. CVSS 3.1 Base Score 4.9 (Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H).
{
"affected": [],
"aliases": [
"CVE-2025-50091"
],
"database_specific": {
"cwe_ids": [
"CWE-400"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-07-15T20:15:45Z",
"severity": "MODERATE"
},
"details": "Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are 8.0.0-8.0.42, 8.4.0-8.4.5 and 9.0.0-9.3.0. Easily exploitable vulnerability allows high privileged attacker with network access via multiple protocols to compromise MySQL Server. Successful attacks of this vulnerability can result in unauthorized ability to cause a hang or frequently repeatable crash (complete DOS) of MySQL Server. CVSS 3.1 Base Score 4.9 (Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H).",
"id": "GHSA-wjxg-4572-7wfg",
"modified": "2025-07-15T21:31:42Z",
"published": "2025-07-15T21:31:42Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-50091"
},
{
"type": "WEB",
"url": "https://www.oracle.com/security-alerts/cpujul2025.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
Mitigation
Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.
Mitigation
- Mitigation of resource exhaustion attacks requires that the target system either:
- The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
- The second solution is simply difficult to effectively institute -- and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
- recognizes the attack and denies that user further access for a given amount of time, or
- uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed.
Mitigation
Ensure that protocols have specific limits of scale placed on them.
Mitigation
Ensure that all failures in resource allocation place the system into a safe posture.
CAPEC-147: XML Ping of the Death
An attacker initiates a resource depletion attack where a large number of small XML messages are delivered at a sufficiently rapid rate to cause a denial of service or crash of the target. Transactions such as repetitive SOAP transactions can deplete resources faster than a simple flooding attack because of the additional resources used by the SOAP protocol and the resources necessary to process SOAP messages. The transactions used are immaterial as long as they cause resource utilization on the target. In other words, this is a normal flooding attack augmented by using messages that will require extra processing on the target.
CAPEC-227: Sustained Client Engagement
An adversary attempts to deny legitimate users access to a resource by continually engaging a specific resource in an attempt to keep the resource tied up as long as possible. The adversary's primary goal is not to crash or flood the target, which would alert defenders; rather it is to repeatedly perform actions or abuse algorithmic flaws such that a given resource is tied up and not available to a legitimate user. By carefully crafting a requests that keep the resource engaged through what is seemingly benign requests, legitimate users are limited or completely denied access to the resource.
CAPEC-492: Regular Expression Exponential Blowup
An adversary may execute an attack on a program that uses a poor Regular Expression(Regex) implementation by choosing input that results in an extreme situation for the Regex. A typical extreme situation operates at exponential time compared to the input size. This is due to most implementations using a Nondeterministic Finite Automaton(NFA) state machine to be built by the Regex algorithm since NFA allows backtracking and thus more complex regular expressions.