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Critical, CVSS 9.2amended

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

CVE-2025-65015GHSA-frfh-8v73-gjg4

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (joserfc 1.4.2, 1.3.5), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • PyPI joserfc

    Affected
    >= 1.3.3, < 1.3.5>= 1.4.0, < 1.4.2
    Fixed in
    1.4.2, 1.3.5

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
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 · score source
EPSS
  • CVE-2025-65015: 0.44% estimated exploitation activity in the next 30 days; percentile 38.27 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary 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.

Details 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 per se. It is therefore the responsibility of the underlying web server…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 6 · amended ·

    Amended from osv record GHSA-frfh-8v73-gjg4

  2. Revision 5 · amended ·

    Amended from ghsa record GHSA-frfh-8v73-gjg4

  3. Revision 4 · amended ·

    Amended from ghsa record GHSA-frfh-8v73-gjg4

  4. Revision 3 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  5. Revision 2 · amended ·

    Amended from osv record GHSA-frfh-8v73-gjg4

  6. Revision 1 · created ·

    Published from ghsa record GHSA-frfh-8v73-gjg4

Agent brief

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# Patch Next advisory brief: CVE-2025-65015

Advisory: joserfc has Possible Uncontrolled Resource Consumption Vulnerability Triggered by Logging Arbitrarily Large JWT Token Payloads
IDs: CVE-2025-65015, GHSA-frfh-8v73-gjg4
Record: https://patchnext.com/advisories/cve-2025-65015 (revision 6, source checked 28 Oct 2026, 06:05 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: joserfc 1.4.2, 1.3.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI joserfc: affected >= 1.3.3, < 1.3.5; >= 1.4.0, < 1.4.2; fixed in 1.4.2, 1.3.5

## Suggested inspection (read-only)
- `python -m pip show joserfc`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on joserfc.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-frfh-8v73-gjg4 (GitHub-reviewed advisory GHSA-frfh-8v73-gjg4 lists affected ranges: PyPI joserfc >=1.3.3 =1.4.0 <1.4.2)
- Verified: https://osv.dev/vulnerability/GHSA-frfh-8v73-gjg4 (OSV record GHSA-frfh-8v73-gjg4 lists affected ranges: PyPI joserfc >=1.3.3 =1.4.0 <1.4.2 (fixed))

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