Vulnerability · Published Oct 29, 2026 · Assigned by GitHub_M
CVE-2026-119284joserfc: Compact JWS size guard allocates attacker-controlled segments before rejection
Medium 6.9
In plain English
A medium-severity uncontrolled resource consumption in joserfc from authlib. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 9% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.7.6, joserfc compact JWS deserialization calls bytes.split() before enforcing the existing aggregate segment-size limits. When attacker-controlled compact serialization bytes reach deserialize_compact(), the split creates copies of the header, payload, and signature segments before ExceededSizeError rejects them, causing an additional allocation approximately proportional to the supplied token. Requests that exhaust available process memory can therefore cause an availability failure even though signature verification fails. This issue is fixed in version 1.7.6.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:13 | joserfc | no fix listed | DEBIAN-CVE-2026-119284 |
| Debian:14 | joserfc | 1.7.7-1 | DEBIAN-CVE-2026-119284 |
| PyPI | joserfc | 1.7.6 | GHSA-9pg5-8c7x-5hfx |
| Ubuntu:26.04:LTS | joserfc | no fix listed | UBUNTU-CVE-2026-119284 |
| Ubuntu:26.10 | joserfc | no fix listed | UBUNTU-CVE-2026-119284 |
Affected products (as reported)
Weakness: CWE-400 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
References
- https://github.com/authlib/joserfc/security/advisories/GHSA-9pg5-8c7x-5hfx x_refsource_CONFIRM
- https://github.com/authlib/joserfc/commit/397e04f4bbce0b94d86e31c1c003f4640af8fb39 x_refsource_MISC
- https://github.com/authlib/joserfc/releases/tag/1.7.6 x_refsource_MISC