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VulnerabilityPublished

CVE-2026-71488: thephpleague commonmark · Inefficient Algorithmic Complexity

Affects thephpleague commonmarkSource CVE Database V5

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Not known to be exploited · CVSS 7.5 High : upgrade to 2.9.0 soon.

Data as of 5 Nov 2026, 00:01 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.6% chance of exploitation in 30 days – higher than 50% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2.9.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 6 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

What to do

Upgrade commonmark and thephpleague/commonmark to 2.9.0.

Affected software

ProductAffectedFixed in
thephpleaguecommonmarkAffected
  • >=0.6.0 <2.9.0
Fixed in
  • 2.9.0
Packagistthephpleague/commonmarkpkg:composer/thephpleague/commonmarkOther threatsAffected
  • <2.9.0 >=0.6.0
Fixed in
  • 2.9.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade thephpleague commonmark to version 2.9.0 or later, where this inefficient algorithmic complexity issue is fixed. No other mitigations are indicated.

Description

league/commonmark is a PHP library for parsing and rendering CommonMark Markdown. From 0.6.0 until 2.9.0, specially crafted Markdown lines can cause the parser to have quadratic time complexity when converting, because several parsing paths repeatedly rescan growing portions of a line to translate between character positions and byte positions, and the Autolink extension can also copy and validate the remaining line at every URL-like prefix, allowing an attacker who can submit Markdown for conversion to consume disproportionate CPU time with a comparatively small request. This issue is fixed in 2.9.0.

References

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