Transformers vulnerable to ReDoS attack through its SETTING_RE variable

Exploitation

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

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

• CVE-2025-3262: 0.49% estimated exploitation activity in the next 30 days; percentile 42.49 (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.

A Regular Expression Denial of Service (ReDoS) vulnerability was discovered in the huggingface/transformers repository, specifically in version 4.49.0. The vulnerability is due to inefficient regular expression complexity in the SETTINGRE variable within the transformers/commands/chat.py file. The regex contains repetition groups and non-optimized quantifiers, leading to exponential backtracking when processing 'almost matching' payloads. This can degrade application performance and potentially result in a denial-of-service (DoS) when handling specially crafted input strings. The issue is fixed in version 4.51.0.

Published by the source

7 Jul 2025, 12:30 UTC

Last modified by the source

7 Jul 2026, 17:56 UTC

Source last checked

26 Oct 2026, 13:32 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-489j-g2vx-39wf

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-489j-g2vx-39wf

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# Patch Next advisory brief: CVE-2025-3262

Advisory: Transformers vulnerable to ReDoS attack through its SETTING_RE variable
IDs: CVE-2025-3262, GHSA-489j-g2vx-39wf
Record: https://patchnext.com/advisories/cve-2025-3262 (revision 2, source checked 26 Oct 2026, 13:32 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: transformers 4.51.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI transformers: affected >= 4.49.0, < 4.51.0; fixed in 4.51.0

## Suggested inspection (read-only)
- `python -m pip show transformers`: 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 transformers.
- 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://osv.dev/vulnerability/GHSA-489j-g2vx-39wf (OSV record GHSA-489j-g2vx-39wf lists affected ranges: PyPI transformers >=4.49.0 <4.51.0 (fixed))
- Verified: https://github.com/advisories/GHSA-489j-g2vx-39wf (GitHub-reviewed advisory GHSA-489j-g2vx-39wf lists affected ranges: PyPI transformers >=4.49.0 <4.51.0)

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