Compact JWS parsing in joserfc allocates memory before size check
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · Low
- Fix status
- Partial Red Hat: 8 without a fix
Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-400.
Summary
joserfc before 1.7.6 is a Python library that implements JOSE standards. Its compact JWS deserialization calls bytes.split() before enforcing segment size limits, so it copies the header, payload and signature segments before rejecting oversized input. An unauthenticated remote attacker who sends large compact serialized tokens can exhaust process memory and cause a denial of service, even though signature verification fails. The flaw is classified as CWE-400.
Written with Claude Haiku 5.5 from the sources below · 2026-10-30
Description from the CNA
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| authlib | joserfc | before 1.7.6 | 1.7.6 | Patch available | CNA |
| — | joserfc (PyPI) | before 1.7.6 | 1.7.6 | Patch available | GHSA-9pg5-8c7x-5hfx |
- joserfc Vendorauthlib Affected before 1.7.6 Fixed in 1.7.6 Patch available CNA
- joserfc (PyPI) Vendor— Affected before 1.7.6 Fixed in 1.7.6 Patch available GHSA-9pg5-8c7x-5hfx
Remediation
Upgrade joserfc on PyPI to version 1.7.6, which fixes the issue. Red Hat lists the following products as affected with no fix available: Exploit Intelligence (no fix planned), Lightspeed Core, Migration Toolkit for Applications 8, OpenShift Lightspeed, Red Hat Ansible Automation Platform 2, Red Hat Enterprise Linux command line assistant, Red Hat OpenShift Virtualization 4 and Red Hat Satellite 6.
Written with Claude Haiku 5.5 from the sources below · 2026-10-30
- Fix · CNA joserfc (authlib) Fixed in 1.7.6
- Fix · GHSA-9pg5-8c7x-5hfx joserfc (PyPI) Fixed in 1.7.6 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Exploit Intelligence | Affected | No fix planned: Out of support scope |
| Lightspeed Core | Affected | No fix yet: Fix deferred |
| Migration Toolkit for Applications 8 | Affected | No fix yet: Fix deferred |
| OpenShift Lightspeed | Affected | No fix yet: Fix deferred |
| Red Hat Ansible Automation Platform 2 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux command line assistant | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Virtualization 4 | Affected | No fix yet: Fix deferred |
| Red Hat Satellite 6 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-29 Threatist record created from CVE-2026-119284
- 2026-10-30 Affected versions changed · Red Hat
- 2026-10-30 CVSS score added · Red Hat
- 2026-10-30 Alias added: GHSA-9pg5-8c7x-5hfx
- 2026-10-30 Fix available: PyPI/[email protected] · GHSA-9pg5-8c7x-5hfx
- 2026-10-30 CVSS score added · GHSA-9pg5-8c7x-5hfx
- 2026-10-30 Weakness changed · GHSA-9pg5-8c7x-5hfx
- 2026-10-30 5 new references · GHSA-9pg5-8c7x-5hfx
- 2026-10-30 CISA SSVC decision points changed
- 2026-10-30 Priority changed: MEDIUM → HIGH
References
More authlib vulnerabilities
- TI-2026-65772 Insufficient verification of data authenticity in Authlib CVSS 3.1CRITICAL 9.8
- TI-2026-74876 Signature verification bypass in joserfc JWS deserialization CVSS 3.1CRITICAL 9.1
- TI-2026-22305 Authlib JWS JWK Header Injection: Signature Verification Bypass CVSS 3.1CRITICAL 9.1
- TI-2025-40202 Resource allocation without limits in authlib joserfc CVSS 4.0CRITICAL 9.2
- TI-2026-36756 joserfc: HS256/HS384/HS512 verify accepts empty/nil HMAC key (cross-language sibling of CVE-2026-45363) CVSS 4.0HIGH 8.7
- TI-2026-79518 Authlib fix bypass lets attackers forge HS256 tokens with PEM keys CVSS 3.1CRITICAL 9.1
Sources
- CVE-2026-119284 · CVE Program
- CVE-2026-119284 · NVD
- FIRST EPSS
- GHSA-9pg5-8c7x-5hfx · GitHub Advisory Database · CC BY 4.0
- CVE-2026-119284 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences