Guzzle OAuth Subscriber has insufficient nonce entropy

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.3 · CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2025-21617: 0.48% estimated exploitation activity in the next 30 days; percentile 41.40 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Nonce generation does not use sufficient entropy nor a cryptographically secure pseudorandom source (https://github.com/guzzle/oauth-subscriber/blob/0.8.0/src/Oauth1.php#L192). This can leave servers vulnerable to replay attacks when TLS is not used. Patches Upgrade to version 0.8.1 or higher. Workarounds No. References Issue is similar to https://nvd.nist.gov/vuln/detail/CVE-2025-22376.

Published by the source

6 Jan 2025, 19:23 UTC

Last modified by the source

15 Jul 2026, 21:57 UTC

Source last checked

26 Oct 2026, 14:50 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-237r-r8m4-4q88

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# Patch Next advisory brief: CVE-2025-21617

Advisory: Guzzle OAuth Subscriber has insufficient nonce entropy
IDs: CVE-2025-21617, GHSA-237r-r8m4-4q88
Record: https://patchnext.com/advisories/cve-2025-21617 (revision 1, source checked 26 Oct 2026, 14:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: guzzlehttp/oauth-subscriber 0.8.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist guzzlehttp/oauth-subscriber: affected < 0.8.1; fixed in 0.8.1

## Suggested inspection (read-only)
- Packagist guzzlehttp/oauth-subscriber: check the installed version with your package manager.

## 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 guzzlehttp/oauth-subscriber.
- 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-237r-r8m4-4q88 (GitHub-reviewed advisory GHSA-237r-r8m4-4q88 lists affected ranges: Packagist guzzlehttp/oauth-subscriber >=0 <0.8.1)

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