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CVE-2025-65015VulnerabilityPublished Updated

joserfc has Possible Uncontrolled Resource Consumption Vulnerability Triggered by Logging Arbitrarily Large JWT Token

Affects joserfcSource GCVE Database

0
Authoritative record:CVE-2025-65015· Critical 9.2

Not known to be exploited · CVSS 9.2 Critical : upgrade to 1.3.5 as a priority.

Data as of 27 Oct 2026, 18:28 UTC

CVSS 4.0 base score
9.2Critical
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 1.3.5, 1.4.2
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 18 Nov 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade joserfc to 1.3.5; joserfc to 1.4.2.

Affected software

ProductAffectedFixed in
PyPIjoserfcAffected
  • >=1.3.3 <1.3.5
Fixed in
  • 1.3.5
PyPIjoserfcAffected
  • >=1.4.0 <1.4.2
Fixed in
  • 1.4.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in joserfc versions 1.3.5 and 1.4.2. Users should upgrade to these or later versions to remediate the vulnerability. Additionally, it is critical to deploy Python web applications behind production-grade web servers or reverse proxies (e.g., uvicorn with appropriate settings, gunicorn, nginx) that enforce strict HTTP header size limits to prevent large JWT tokens from reaching the application. Without such infrastructure, the application remains vulnerable regardless of joserfc version.

Description

The joserfc library versions 1.3.3 up to but not including 1.3.5 and 1.4.0 up to but not including 1.4.2 contain a vulnerability where logging or diagnostic tools may process arbitrarily large JWT tokens embedded in exception messages. This can lead to uncontrolled resource consumption when a maliciously crafted large JWT token is sent to a Python web application that does not have proper HTTP header size limits enforced by its web server or reverse proxy.

References

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