Skip to content
Fencer Vulns
critical 9.1

CVE-2026-28802 json

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

published 2026-03-04 8 mo ago modified 2026-09-10 59 d ago also GHSA-7wc2-qxgw-g8gg , PYSEC-2026-2118 , EUVD-2026-10009

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

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
8 mo ago

Exploit prediction

0.54% chance of exploitation in the next 30 days, higher than 45% of all scored CVEs (FIRST EPSS, 2026-11-08).

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 Vulns 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.