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TI-2026-44996 Aliases CVE-2026-62995

joserfc accepts JWT with padding, leading to JWT malleability

Priority LOW 19CWE-345Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Attack requirements
Present
Impact type
Security bypass
Confidentiality · integrity · availability
None · Low · None
Fix status
Partial Red Hat: 1 fixed, 6 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-345.

Summary

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. in versions 1.7.1 and prior, joserfc accepts JWTs with trailing padding (==) which are not conforming to the JOSE specifications. This leads to malleability of the JWTs when consumed by joserfc. Depending on this application this might or not be an issue. This could lead to bypass of token revocation or anti-replay protection when implemented as a deny list of tokens or a deny list of token hashes. Note that ECDSA JWS are always malleable because of the malleability of ECDSA signatures (first test case in the code bellow). This makes a scheme which assumes that JWTs are not malleable brittle. However for other signatures (or MAC) schemes it might make sense to assume non malleability of the token. This issue has been fixed in version 1.7.2.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00145 3rd percentileScored 2026-11-07
Fix Partial joserfc (authlib): 1.7.2Red Hat: 1 advisoryRed Hat: 1 fixed, 6 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
authlibjoserfcbefore 1.7.21.7.2Patch availableCNA
  • joserfc Vendorauthlib Affected before 1.7.2 Fixed in 1.7.2 Patch available CNA

Remediation

  • Fix · CNA joserfc (authlib) Fixed in 1.7.2

Red Hat 1 advisory

  • RHSA-2026:48758 Released 2026-07-30 · Red Hat rating Important
    Red Hat Hardened Images RPMs Security Update
    • Red Hat Hardened Images jaeger-2.20.0-0.8.hum1@aarch64, jaeger-2.20.0-0.8.hum1@src, jaeger-2.20.0-0.8.hum1@x86_64

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Lightspeed CoreAffectedNo fix yet: Fix deferred
Migration Toolkit for Applications 8AffectedNo fix yet: Fix deferred
OpenShift LightspeedAffectedNo fix yet: Fix deferred
Red Hat Ansible Automation Platform 2AffectedNo fix yet: Fix deferred
Red Hat OpenShift Virtualization 4AffectedNo fix yet: Fix deferred
Red Hat Satellite 6AffectedNo fix yet: Fix deferred
Red Hat Hardened ImagesFixed RHSA-2026:48758
Not affected: 1 product
  • Red Hat Enterprise Linux command line assistant

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-62995

References

Other 1

  • 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
See all 30 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences