Bleach linkify(parse_email=True) CPU exhaustion via unbounded email regex scanning

Exploitation

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

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary Bleach 6.3.0 exposes a documented email-linkification path through bleach.linkify(..., parseemail=True). The implementation scans attacker-controlled text with EMAILRE.finditer() over the full character token and has no length, timeout, or linear prefilter before applying the dot-atom email regex. A non-email payload around 30 KB causes multi-second CPU consumption per request/call, creating a direct availability risk for applications that enable email linkification on user-submitted text. Affected Product - Package: bleach - Ecosystem: pip - Affected versions: verified in 6.3.0; exact first affected version not established - Patched versions: none known at finalization time - Tested version: 6.3.0 - Audit commit/tag: v6.3.0 / 5546d5dbce60d08ccb99d981778d74044d646d4e - PyPI sdist SHA256: 6f3b91b1c0a02bb9a78b5a454c92506aa0fdf197e1d5e114d2e00c6f64306d22 Vulnerability Details - CWE: CWE-1333: Inefficient Regular Expression Complexity; related availability impact maps to CWE-400…

Published by the source

16 Jun 2026, 14:07 UTC

Last modified by the source

16 Jun 2026, 14:15 UTC

Source last checked

26 Oct 2026, 13:45 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-g75f-g53v-794x

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-g75f-g53v-794x

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: GHSA-g75f-g53v-794x

Advisory: Bleach linkify(parse_email=True) CPU exhaustion via unbounded email regex scanning
IDs: GHSA-g75f-g53v-794x
Record: https://patchnext.com/advisories/ghsa-g75f-g53v-794x (revision 2, source checked 26 Oct 2026, 13:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI bleach: affected >= 6.3.0, <= 6.3.0

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

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on bleach.
- 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-g75f-g53v-794x (OSV record GHSA-g75f-g53v-794x lists affected ranges: PyPI bleach >=6.3.0 <=6.3.0)
- Verified: https://github.com/advisories/GHSA-g75f-g53v-794x (GitHub-reviewed advisory GHSA-g75f-g53v-794x lists affected ranges: PyPI bleach >=6.3.0 <=6.3.0)

Commands are suggestions: review each one before running it.