What is CVE-2026-71488?
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.
The record classifies CVE-2026-71488 under weakness classes CWE-407, CWE-1050. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 60 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 7.5 — HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - EPSS (FIRST)
- 0.3% probability of exploitation in the next 30 days, higher than 27.2% of all scored CVEs
- CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 4.8/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-08-06, last modified 2026-08-07
Is CVE-2026-71488 being exploited?
It currently carries a trending score of 36 in the Threadlinqs vulnerability feed.
Affected products and versions
- thephpleague: commonmark
Affected software packages:
composer:league/commonmark— patched in 2.9.0
How to fix CVE-2026-71488
Fixed versions are recorded for 1 package: composer:league/commonmark 2.9.0. No vendor patch reference has been recorded for CVE-2026-71488 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.
Threat activity tracking CVE-2026-71488
No threat campaign in the Threadlinqs corpus currently references CVE-2026-71488, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.
Sources
Enriched from CVE.org, FIRST EPSS, GitHub Security Advisories, NVD. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.