---
title: "CVE-2025-65015: joserfc has Possible Uncontrolled Resource Consumption Vulnerability Triggered by Logging Arbitrarily Large JWT Token Payloads"
url: https://erroneo.us/security/cve/CVE-2025-65015/
description: "CVE-2025-65015 (joserfc (PyPI)): joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards.…"
type: vulnerability-record
section: "Security Digest"
date_published: 2025-11-18
date_modified: 2025-11-19
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2025-65015"
kev: false
cvss: 9.2
epss: 0.0044
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2025-65015: joserfc has Possible Uncontrolled Resource Consumption Vulnerability Triggered by Logging Arbitrarily Large JWT Token Payloads

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.4% , percentile 37: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 37% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes joserfc (PyPI) >= 1.3.3, < 1.3.5, fixed in 1.3.5 ; joserfc (PyPI) >= 1.4.0, < 1.4.2, fixed in 1.4.2 . Check your lockfile, including transitive dependencies.

## What it is

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.

## Affected packages

- PyPI `joserfc` >= 1.3.3, < 1.3.5 → fixed: 1.3.5
- PyPI `joserfc` >= 1.4.0, < 1.4.2 → fixed: 1.4.2

## Affected products (CVE record)

- authlib joserfc: >= 1.3.3, < 1.3.5, >= 1.4.0, < 1.4.2

## Severity

- GitHub_M CVSS 4.0: 9.2 `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`
- GitHub CVSS 4.0: 9.2 `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

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable yes , technical impact partial .
- FIRST EPSS (model of 2026-10-21): 0.44% probability of exploitation activity in the next 30 days; percentile 37.

## Sources

- [GitHub Advisory GHSA-frfh-8v73-gjg4](https://github.com/advisories/GHSA-frfh-8v73-gjg4)
- [CVE.org record CVE-2025-65015](https://www.cve.org/CVERecord?id=CVE-2025-65015)
- [NVD entry CVE-2025-65015](https://nvd.nist.gov/vuln/detail/CVE-2025-65015)
- [github.com](https://github.com/authlib/joserfc/security/advisories/GHSA-frfh-8v73-gjg4)
- [github.com](https://github.com/authlib/joserfc/commit/63932f169d924caffafa761af2122b82059017f7)
- [github.com](https://github.com/authlib/joserfc/commit/673c8743fd0605b0e1de6452be6cba75f44e466b)
- [github.com](https://github.com/authlib/joserfc/releases/tag/1.3.5)
- [github.com](https://github.com/authlib/joserfc/releases/tag/1.4.2)

---
Source page: https://erroneo.us/security/cve/CVE-2025-65015/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt