Vigie VulnDBEuropean-hosted Vulnerability DB

CVE-2026-28802

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

At a glance

Severity
HIGH 7.7
EPSS
EPSS 0.50 % · percentile 43 (2026-10-27)
State
PUBLISHED
Published
Updated
Assigner
GitHub_M
NVD status
Modified

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.

Scores

VersionScoreVectorScored by
CVSS 4.0HIGH 7.7CVSS: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:PGitHub_M
CVSS 3.1CRITICAL 9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Nredhat-SADP
CVSS 4.0HIGH 7.7CVSS: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:XNVD · security-advisories@github.com (Secondary)
CVSS 3.1CRITICAL 9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HNVD · nvd@nist.gov (Primary)
CVSS 3.1CRITICAL 9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NNVD · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c (Secondary)

Weaknesses (CWE)

Advisories

European references

Affected configurations (NVD CPE)

Affected products

ProductVersions
authlib · authlibaffected >= 1.6.5, < 1.6.7

References

Sources

SourceLicence
CVE List (CVEProject cvelistV5)CVE Program Terms of Use
EPSS (FIRST.org)FIRST — attribution requested
ENISA EUVDENISA — reproduction authorised, source acknowledged
NVD (NIST) via fkie-cad/nvd-json-data-feedsPublic domain — this product uses data from the NVD API but is not endorsed or certified by the NVD