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Vulnerability record · CVE-2026-86433 · published 7 September 2026

CVE-2026-86433: commonmark versions from 1.5.0 before 2.8.4 contain a denial of service vulnerability in the Attributes extens…

commonmark versions from 1.5.0 before 2.8.4 contain a denial of service vulnerability in the Attributes extension where AttributesListener::findTargetAndDirection() performs quadratic-time sibling list scanning. Unauthenticated attackers can submit approximately 32 KB of repeated attribute blocks to cause parsing to take over 5 seconds, exhausting server resources.

8.7 CVSS 4.0 High EPSS 0.51% · top 58.9% CWE-407 · CWE-407 Awaiting Analysis
8.7CVSS 4.0 base score
0.51%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
2References
8 Sep 2026Last modified by NVD

Description

commonmark versions from 1.5.0 before 2.8.4 contain a denial of service vulnerability in the Attributes extension where AttributesListener::findTargetAndDirection() performs quadratic-time sibling list scanning. Unauthenticated attackers can submit approximately 32 KB of repeated attribute blocks to cause parsing to take over 5 seconds, exhausting server resources.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/thephpleague/commonmark/security/advisories/GHSA-g2gp-3wwq-f4ph
https://www.vulncheck.com/advisories/commonmark-1.5.0-before-2.8.4-denial-of-service-via-attributes

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Source: NIST National Vulnerability Database (record CVE-2026-86433), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.