CVE-2026-33948 — jq: Embedded-NUL Truncation in CLI JSON Input Path Causes Prefix-Only Validation of Malformed Input

Affected: jqlang jq

jq is a command-line JSON processor. Commits before 6374ae0bcdfe33a18eb0ae6db28493b1f34a0a5b contain a vulnerability where CLI input parsing allows validation bypass via embedded NUL bytes. When reading JSON from files or stdin, jq uses strlen() to determine buffer length instead of the actual byte count from fgets(), causing it to truncate input at the first NUL byte and parse only the preceding prefix. This enables an attacker to craft input with a benign JSON prefix before a NUL byte followed by malicious trailing data, where jq validates only the prefix as valid JSON while silently discarding the suffix. Workflows relying on jq to validate untrusted JSON before forwarding it to downstream consumers are susceptible to parser differential attacks, as those consumers may process the full input including the malicious trailing bytes. This issue has been patched by commit 6374ae0bcdfe33a18eb0ae6db28493b1f34a0a5b.

USN-8202-1 — jq vulnerabilities

Affected: Ubuntu:Pro:14.04:LTS: jq, Ubuntu:Pro:16.04:LTS: jq, Ubuntu:Pro:18.04:LTS: jq, Ubuntu:Pro:20.04:LTS: jq, Ubuntu:22.04:LTS: jq, Ubuntu:24.04:LTS: jq, Ubuntu:25.10: jq

It was discovered that jq did not correctly handle certain string concatenations. An attacker could possibly use this issue to cause a denial of service or execute arbitrary code. This issue was addressed in Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS and Ubuntu 25.10. (CVE-2026-32316)

It was discovered that jq did not correctly handle recursion in certain circumstances. An attacker could possibly use this issue to cause a denial of service. (CVE-2026-33947)

It was discovered that jq did not correctly handle improperly terminated strings. An attacker could possibly use this issue to cause a denial of service or execute arbitrary code. This issue was addressed in Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS and Ubuntu 25.10. (CVE-2026-33948)

It was discovered that jq did not correctly handle checking certain variable types. An attacker could possibly use this issue to cause a denial of service or leak sensitive information. This issue was addressed in Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS and Ubuntu 25.10. (CVE-2026-39956)

It was discovered that jq did not correctly handle certain string formatting. An attacker could possibly use this issue to leak sensitive information or cause a denial of service. (CVE-2026-39979)

It was discovered that jq used a fixed seed for hash table operations. An attacker could possibly use this issue to cau…

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CVE-2026-33948 — jq: Embedded-NUL Truncation in CLI JSON Input Path Causes Prefix-Only Validation of Malformed Input

USN-8202-1 — jq vulnerabilities