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Fencer Intel
critical 9.1

CVE-2026-28802 json

Authlib: Setting `alg: none` and a blank signature appears to bypass signature verification

published 8mo ago modified last mo. also EUVD-2026-10009 , GHSA-7wc2-qxgw-g8gg , PYSEC-2026-2118

cvss
9.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 45%
public exploits
0
none known

Summary

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.

Patch / fix

  • pypi authlib 1.6.7
  • Red Hat Red Hat Ansible Automation Platform 2.6 1774417022
  • Red Hat Red Hat Quay 3.10 1773971077
  • Red Hat Red Hat Quay 3.12 1773771962
  • Red Hat Red Hat Quay 3.15 1775169219
  • Red Hat Red Hat Quay 3.16 1779204086
  • Red Hat Red Hat Quay 3.9 1773936323
  • python-authlib Debian 14 1.6.7-1

debian advisories DEBIAN-CVE-2026-28802

Is CVE-2026-28802 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-28802 updated cvss 9.1

authlib: Authlib: Signature verification bypass via malicious JWT allows unauthorized access

  • Red Hat Satellite 6 satellite/foreman-mcp-server-rhel9
    affected: workaround, no fix available
  • Red Hat Ansible Automation Platform 2.6 ansible-automation-platform-26 1774417022
    fixed: vendor fix RHSA-2026:6309
  • Red Hat Quay 3.9 quay 1773936323
    fixed: vendor fix RHSA-2026:5168
  • Red Hat Quay 3.10 quay 1773971077
    fixed: vendor fix RHSA-2026:5665
  • Red Hat Quay 3.12 quay 1773771962
    fixed: vendor fix RHSA-2026:4942
  • Red Hat Quay 3.15 quay 1775169219
    fixed: vendor fix RHSA-2026:6568
  • Red Hat Quay 3.16 quay 1779204086
    fixed: vendor fix RHSA-2026:19375
  • Red Hat Ansible Automation Platform 2.6 ansible-automation-platform 1774648896, ansible-automation-platform 1774648925, ansible-automation-platform-26 1774139204, ansible-automation-platform-26 1774139334, ansible-automation-platform-26 1774153089, ansible-automation-platform-26 1774243862, +22 more Red Hat Quay 3.9 quay 1772725093, quay 1772728539, quay 1772739181, quay 1773931180, quay 1773931187, quay 1773931200, +3 more Red Hat Quay 3.10 quay 1772725047, quay 1772726823, quay 1772739218, quay 1774021695, quay 1774021704, quay 1774021722, +3 more Red Hat Quay 3.12 quay 1772054192, quay 1772054202, quay 1772132933, quay 1773761676, quay 1773765467, quay 1773765477, +3 more Red Hat Quay 3.15 quay 1774979159, quay 1774979227, quay 1774980222, quay 1774980224, quay 1774984603, quay 1775183105, +3 more Red Hat Quay 3.16 quay 1778704509, quay 1778704515, quay 1778704550, quay 1778704556, quay 1778705015, quay 1778705065, +3 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
8mo ago

Exploit prediction

0.54% chance of exploitation in the next 30 days, higher than 45% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/authlib/authlib/security/advisories/GHSA-7wc2-qxgw-g8gg referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 7.7 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/E:P
CISA ADP 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CNA 4.0 7.7 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/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
OSV 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
pypi authlib
>=1.6.5, <1.6.7
1.6.7

Affected products

  • authlib authlib
  • Red Hat Red Hat Ansible Automation Platform 2.6
  • Red Hat Red Hat Quay 3.10
  • Red Hat Red Hat Quay 3.12
  • Red Hat Red Hat Quay 3.15
  • Red Hat Red Hat Quay 3.16
  • Red Hat Red Hat Quay 3.9
  • Red Hat Red Hat Satellite 6

Classification

Weakness
  • CWE-347 Improper Verification of Cryptographic Signature

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.