CVE-2025-65015

CRITICAL EPSS 24.7%
Published Nov 18, 20257mo ago · Modified Jun 17, 20261w ago
9.2 CVSS 4.0
Critical
Find Similar
Published Nov 18, 2025 7mo ago
Last Modified Jun 17, 2026 1w ago

Description

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. In versions from 1.3.3 to before 1.3.5 and from 1.4.0 to before 1.4.2, the ExceededSizeError exception messages are embedded with non-decoded JWT token parts and may cause Python logging to record an arbitrarily large, forged JWT payload. In situations where a misconfigured — or entirely absent — production-grade web server sits in front of a Python web application, an attacker may be able to send arbitrarily large bearer tokens in the HTTP request headers. When this occurs, Python logging or diagnostic tools (e.g., Sentry) may end up processing extremely large log messages containing the full JWT header during the joserfc.jwt.decode() operation. The same behavior also appears when validating claims and signature payload sizes, as the library raises joserfc.errors.ExceededSizeError() with the full payload embedded in the exception message. Since the payload is already fully loaded into memory at this stage, the library cannot prevent or reject it. This issue has been patched in versions 1.3.5 and 1.4.2.

CVSS Details

Base Score
9.2
Exploitability
—
Impact
—
Vector string
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/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
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope X

Threat Intelligence

EPSS Exploit Probability
24.7% percentile
Exploit & Patch Status
Public Exploit Known
Patch Available

Weaknesses 1

CWE-770

Affected Products 2

VendorProductVersionRange
hsiaomingjoserfc*≥1.3.3  –  <1.3.5
hsiaomingjoserfc*≥1.4.0  –  <1.4.2

References 5

  • github.com https://github.com/authlib/joserfc/commit/63932f169d924caffafa761af2122b82059017f7
    Patch
  • github.com https://github.com/authlib/joserfc/commit/673c8743fd0605b0e1de6452be6cba75f44e466b
    Patch
  • github.com https://github.com/authlib/joserfc/releases/tag/1.3.5
    Release Notes
  • github.com https://github.com/authlib/joserfc/releases/tag/1.4.2
    Release Notes
  • github.com https://github.com/authlib/joserfc/security/advisories/GHSA-frfh-8v73-gjg4
    ExploitVendor Advisory

Remediation

  • github.com https://github.com/authlib/joserfc/commit/63932f169d924caffafa761af2122b82059017f7
    Patch
  • github.com https://github.com/authlib/joserfc/commit/673c8743fd0605b0e1de6452be6cba75f44e466b
    Patch