CyberSecBulletin
CVE-2026-28802NVD status: Modified

authlib: Improper Verification of Cryptographic Signature

Published Updated By the CyberSecBulletin desk

CVE-2026-28802 is a critical-severity improper verification of cryptographic signature vulnerability in authlib, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected authlib versions: >= 1.6.5, < 1.6.7. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.54% chance of exploitation within 30 days, which is low compared with other CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Check which version of authlib you run against the affected versions below, and install the vendor's latest release.
  2. Read the advisory on github.com for workarounds and exact fixed builds.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Authlibauthlib>= 1.6.5, < 1.6.7Not stated
Red HatRed Hat Ansible Automation Platform 2.6Not specified in the recordNot stated
Red HatRed Hat Quay 3.10Not specified in the recordNot stated
Red HatRed Hat Quay 3.12Not specified in the recordNot stated
Red HatRed Hat Quay 3.15Not specified in the recordNot stated
Red HatRed Hat Quay 3.16Not specified in the recordNot stated
Red HatRed Hat Quay 3.9Not specified in the recordNot stated
Red HatRed Hat Satellite 6Not specified in the recordNot stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 4.07.7HighCNA (github.com)
CVSS 3.19.8CriticalNVD
CVSS 3.19.1CriticalCNA

Official description

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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Verification of Cryptographic Signature

The product does not verify, or incorrectly verifies, the cryptographic signature for data.

More Improper Verification of Cryptographic Signature vulnerabilities (CWE-347)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in authlib

All authlib vulnerabilities

Recent Improper Verification of Cryptographic Signature vulnerabilities

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