Bug 2445120 (CVE-2026-28802)

Summary: CVE-2026-28802 authlib: Authlib: Signature verification bypass via malicious JWT allows unauthorized access
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: anthomas, bdettelb, dfreiber, doconnor, drow, dschmidt, ebourniv, ehelms, erezende, ggainey, hasun, jburrell, jlanda, juwatts, jwong, kshier, lgallett, mhulan, nmoumoul, nyancey, omaciel, osousa, pcreech, ptisnovs, rchan, sbunciak, simaishi, smallamp, smcdonal, stcannon, teagle, tmalecek, ttakamiy, vkumar, yguenane
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Authlib, a Python library for building OAuth and OpenID Connect servers. A remote attacker can exploit this vulnerability by crafting a malicious JSON Web Token (JWT) with a "none" algorithm and an empty signature. This bypasses the expected signature verification, potentially allowing the attacker to forge tokens and gain unauthorized access or perform unauthorized actions within applications using Authlib.
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Description OSIDB Bzimport 2026-03-06 07:02:12 UTC
Authlib is a Python library which builds OAuth and OpenID Connect servers. From version 1.6.5 to before version 1.6.7, previous tests involving passing a malicious JWT containing alg: none and an empty signature was passing the signature verification step without any changes to the application code when a failure was expected.. This issue has been patched in version 1.6.7.