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CVE-2026-67422

CVE-2026-67422 · pymdown-extensions: Exponential-backtracking ReDoS in caret, tilde, betterem, and magiclink inline processors

This page contains facts from public vulnerability sources. Check the original advisory before updating.

pymdown-extensions is a collection of extensions for the Python Markdown library. In versions up to and including 11.0, four inline processors (caret, tilde, betterem, and magiclink) use regular expressions whose content groups can partition a run of delimiter characters in exponentially many ways, causing catastrophic backtracking. As a result, a single untrusted Markdown line under 50 bytes rendered with markdown.markdown() in each extension's default configuration drives the rendering thread into unbounded CPU usage that grows exponentially with input length, enabling an unauthenticated remote attacker who can submit Markdown to cause denial of service. The exposure is concrete for web applications that render user-supplied Markdown (comments, wikis, issue bodies, live preview), including any app using pymdownx.extra which bundles the vulnerable betterem default, as well as hosted docs/CI systems that build untrusted Markdown. The issue has been fixed in version 11.0.1.

CVSS 7.5 · High · EPSS 0.6% · Fix available

Published
Updated

Stack: system · python

Affected products and versions

  • pymdown-extensions

    Versions
    • < 11.0.1: Affected

    No fix published

  • pymdown-extensions Debian:12

    Versions
    • 10.11.2-1
    • 10.13-1
    • 10.13-2
    • 10.13-3
    • 10.13-4
    • 10.19.1-1
    • 10.19.1-3
    • 10.8.1-1
    • 10.9-1
    • 11.0.1-1
    • 9.5-2
    • 9.5-3
    • 9.5-4
    • 9.5-5
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • pymdown-extensions Debian:13

    Versions
    • 10.13-1
    • 10.13-1+deb13u1
    • 10.13-2
    • 10.13-3
    • 10.13-4
    • 10.19.1-1
    • 10.19.1-3
    • 11.0.1-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • pymdown-extensions Debian:14

    Versions
    • 10.13-1
    • 10.13-2
    • 10.13-3
    • 10.13-4
    • 10.19.1-1
    • 10.19.1-3
    Affected ranges
    • ECOSYSTEM: < 11.0.1-1

    Update to 11.0.1-1

  • pymdown-extensions PyPI

    Versions
    • 1.0.0
    • 1.0.1
    • 1.1
    • 1.2
    • 1.3
    • 1.4
    • 1.5
    • 1.6
    • 1.6.1
    • 1.7
    • 1.8
    • 10.0
    • 10.0.1
    • 10.1
    • 10.10
    • 10.10.1
    • 10.10.2
    • 10.11
    • 10.11.1
    • 10.11.2
    • 10.12
    • 10.13
    • 10.14
    • 10.14.1
    • 10.14.2
    • 10.14.3
    • 10.15
    • 10.16
    • 10.16.1
    • 10.17
    • 10.17.1
    • 10.17.2
    • 10.18
    • 10.19
    • 10.19.1
    • 10.2
    • 10.2.1
    • 10.20
    • 10.20.1
    • 10.21
    • 10.21.2
    • 10.21.3
    • 10.3
    • 10.3.1
    • 10.4
    • 10.5
    • 10.6
    • 10.7
    • 10.7.1
    • 10.8
    • 10.8.1
    • 10.9
    • 11.0
    • 2.0
    • 3.0
    • 3.1
    • 3.2
    • 3.2.1
    • 3.3
    • 3.4
    • 3.5
    • 4.0
    • 4.1
    • 4.10
    • 4.10.1
    • 4.10.2
    • 4.11
    • 4.12
    • 4.2
    • 4.3
    • 4.4
    • 4.5
    • 4.5.1
    • 4.6
    • 4.7
    • 4.8
    • 4.9
    • 4.9.1
    • 4.9.2
    • 5.0
    • 6.0
    • 6.1
    • 6.2
    • 6.2.1
    • 6.3
    • 7.0
    • 7.0b1
    • 7.0b2
    • 7.0rc1
    • 7.0rc2
    • 7.1
    • 8.0
    • 8.0.1
    • 8.1
    • 8.1.1
    • 8.2
    • 9.0
    • 9.0.dev0
    • 9.1
    • 9.10
    • 9.10a1
    • 9.10a2
    • 9.10a3
    • 9.10b1
    • 9.10b2
    • 9.10b3
    • 9.10b4
    • 9.10b5
    • 9.11
    • 9.2
    • 9.3
    • 9.4
    • 9.5
    • 9.6
    • 9.7
    • 9.8
    • 9.9
    • 9.9.1
    • 9.9.2
    Affected ranges
    • ECOSYSTEM: < 11.0.1

    Update to 11.0.1

  • pymdown-extensions Ubuntu:24.04:LTS

    Versions
    • 9.5-2
    • 9.5-4
    • 9.5-5
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • pymdown-extensions Ubuntu:26.04:LTS

    Versions
    • 10.13-3
    • 10.13-4
    • 10.19.1-3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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