Answer in brief
CVE-2026-28498 records a High severity (CVSS 7.5) vulnerability in Authlib: Fail-Open Cryptographic Verification in OIDC Hash Binding. The current sources do not mark it as known exploited. The current feed maps authlib/authlib (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
Answer in brief
CVE-2026-28498 records a High severity (CVSS 7.5) vulnerability in Authlib: Fail-Open Cryptographic Verification in OIDC Hash Binding. The current sources do not mark it as known exploited. The current feed maps authlib/authlib (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps authlib/authlib (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| authlib/authlibgeneric | < 1.6.9 | Not reported |
Published upstream
Mar 16, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 3, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 1, 2026
Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a library-level vulnerability was identified in the Authlib Python library concerning the validation of OpenID Connect (OIDC) ID Tokens. Specifically, the internal hash verification logic (_verify_hash) responsible for validating the at_hash (Access Token Hash) and c_hash (Authorization Code Hash) claims exhibits a fail-open behavior when encountering an unsupported or unknown cryptographic algorithm. This flaw allows an attacker to bypass mandatory integrity protections by supplying a forged ID Token with a deliberately unrecognized alg header parameter. The library intercepts the unsupported state and silently returns True (validation passed), inherently violating fundamental cryptographic design principles and direct OIDC specifications. This issue has been patched in version 1.6.9.
Quoted source text, attributed separately from HOL analysis.
CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps authlib/authlib (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| authlib/authlibgeneric | < 1.6.9 | Not reported |
Published upstream
Mar 16, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 3, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 1, 2026
Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a library-level vulnerability was identified in the Authlib Python library concerning the validation of OpenID Connect (OIDC) ID Tokens. Specifically, the internal hash verification logic (_verify_hash) responsible for validating the at_hash (Access Token Hash) and c_hash (Authorization Code Hash) claims exhibits a fail-open behavior when encountering an unsupported or unknown cryptographic algorithm. This flaw allows an attacker to bypass mandatory integrity protections by supplying a forged ID Token with a deliberately unrecognized alg header parameter. The library intercepts the unsupported state and silently returns True (validation passed), inherently violating fundamental cryptographic design principles and direct OIDC specifications. This issue has been patched in version 1.6.9.
Quoted source text, attributed separately from HOL analysis.