CVE-2026-49852 (GCVE-0-2026-49852)

Vulnerability from cvelistv5 – Published: 2026-07-17 19:14 – Updated: 2026-07-20 14:58
VLAI
Title
joserfc: HS256/HS384/HS512 verify accepts empty/nil HMAC key (cross-language sibling of CVE-2026-45363)
Summary
joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.6.8, joserfc.jwt.decode accepts attacker-forged HMAC-signed tokens when the caller-supplied verification key is the empty string or None, because HMACAlgorithm.sign and HMACAlgorithm.verify in src/joserfc/_rfc7518/jws_algs.py pass the output of OctKey.get_op_key(...) to hmac.new(...) and OctKey.import_key in src/joserfc/_rfc7518/oct_key.py only emits a SecurityWarning for keys shorter than 14 bytes without rejecting zero-length input. This issue is fixed in version 1.6.8.
Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
SSVC
Exploitation: poc Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-07-20 14:58 UTC
CWE
  • CWE-287 - Improper Authentication
  • CWE-326 - Inadequate Encryption Strength
  • CWE-1391 - Use of Weak Credentials
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 7659 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
authlib joserfc Affected: < 1.6.8
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

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