joserfc: b64=false RFC7797 JWS payloads bypass JWSRegistry payload-size limits during deserialization

Description

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. In versions 1.3.4 through 1.6.5, joserfc accepts oversized RFC7797 b64=false JWS payloads without applying JWSRegistry.max_payload_length, which can lead to resource exhaustion. The normal JWS compact and flattened JSON paths reject payloads above the configured payload-size limit with ExceededSizeError. The RFC7797 unencoded payload paths do not make the same check. A valid b64=false compact or flattened JSON JWS can therefore deserialize successfully with a payload larger than JWSRegistry.max_payload_length. Applications that accept lower-trust JWS values and rely on joserfc to reject oversized token content during verification have a moderate availability risk. This issue has been fixed in version 1.6.7.

Scores

EPSS (exploitation in 30 days)

0.24% · top 85% of all CVEs (5 Nov 2026)

CISA SSVC

Exploitation: poc · Automatable: yes · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.3.

Weakness

• CWE-400: Uncontrolled Resource Consumption (opens in a new tab)All about CWE-400 and its CVEs
• CWE-770: Allocation of Resources Without Limits or Throttling (opens in a new tab)All about CWE-770 and its CVEs

Affected products

• authlib · joserfc

  • affected < 1.6.7

Affected packages

From reviewed advisories of the GitHub Advisory Database.

• PyPIjoserfcGHSA-wphv-vfrh-23q5 (opens in a new tab)

References (2)

• https://github.com/authlib/joserfc/security/advisories/GHSA-wphv-vfrh-23q5 (opens in a new tab)x_refsource_CONFIRMexploit
• https://github.com/authlib/joserfc/releases/tag/1.6.7 (opens in a new tab)x_refsource_MISC

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisory GHSA-wphv-vfrh-23q5 (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-48990](https://trackcve.app/badge/CVE-2026-48990.svg)](https://trackcve.app/cve/CVE-2026-48990)

Record last updated 18 Jun 2026, 12:51 UTC.