CVE-2026-49852
joserfc: HS256/HS384/HS512 verify accepts empty/nil HMAC key (cross-language sibling of CVE-2026-45363)
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Description
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.
Remediation
No guide yetNo remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.
References (3)
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