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Fencer Intel
medium 6.5

CVE-2026-28490 json

Authlib Vulnerable to JWE RSA1_5 Bleichenbacher Padding Oracle

published 7mo ago modified 3mo ago also EUVD-2026-12480 , GHSA-7432-952r-cw78 , PYSEC-2026-2116

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 3%
public exploits
0
none known

Summary

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a cryptographic padding oracle vulnerability was identified in the Authlib Python library concerning the implementation of the JSON Web Encryption (JWE) RSA1_5 key management algorithm. Authlib registers RSA1_5 in its default algorithm registry without requiring explicit opt-in, and actively destroys the constant-time Bleichenbacher mitigation that the underlying cryptography library implements correctly. This issue has been patched in version 1.6.9.

Patch / fix

  • pypi authlib 1.6.9
  • authlib authlib 1.6.9
  • python-authlib Debian 12 1.2.0-1+deb12u2
  • python-authlib Debian 14 1.6.9-1

debian advisories DEBIAN-CVE-2026-28490

  • python-authlib Ubuntu Pro 22.04 LTS 0.15.5-1ubuntu0.1~esm2
  • python-authlib Ubuntu Pro 24.04 LTS 1.3.0-1ubuntu0.1~esm2
  • python-authlib Ubuntu Pro 26.04 LTS 1.6.7-1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2026-28490

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • python-Authlib SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Python 3 15 SP7 +1 more 1.3.1-150600.3.17.1

suse advisories SUSE-SU-2026:0975-1

  • python-Authlib openSUSE Leap 16.0 1.5.2-bp160.3.1

opensuse advisories openSUSE-SU-2026:20392-1

Is CVE-2026-28490 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-2026-28490 updated cvss 5.9

authlib: Authlib: Information disclosure due to cryptographic padding oracle in JWE RSA1_5

  • Red Hat Ansible Automation Platform 2 ansible-automation-platform-25/lightspeed-chatbot-rhel8, ansible-automation-platform-26/lightspeed-chatbot-rhel9 Red Hat OpenShift AI (RHOAI) rhoai/odh-mlflow-rhel9, rhoai/odh-pipeline-runtime-minimal-cpu-py312-rhel9, rhoai/odh-pipeline-runtime-pytorch-cuda-py312-rhel9, rhoai/odh-pipeline-runtime-pytorch-rocm-py312-rhel9, rhoai/odh-workbench-jupyter-minimal-cpu-py312-rhel9, rhoai/odh-workbench-jupyter-minimal-cuda-py312-rhel9, +13 more Red Hat Quay 3 quay/quay-rhel8, quay/quay-rhel9 Red Hat Satellite 6 satellite/foreman-mcp-server-rhel9
    affected: no fix available “Fix deferred”
  • Red Hat Lightspeed Core lightspeed-core/lightspeed-stack-rhel9
    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
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
7mo ago

Exploit prediction

0.14% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/authlib/authlib/security/advisories/GHSA-7432-952r-cw78 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 8.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N
CNA 4.0 8.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/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 6.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N
OSV 3.1 6.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N

Affected packages

ecosystem package affected fixed in
pypi authlib
<1.6.9
1.6.9

Affected products

  • authlib authlib

Classification

Weakness
  • CWE-203 Observable Discrepancy
  • CWE-327 Use of a Broken or Risky Cryptographic Algorithm

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.