CVE-2026-86432: Asymmetric Resource Consumption (Amplification) in thephpleague commonmark
Description
commonmark versions from 2.0.0 before 2.8.4 contain a denial of service vulnerability in XmlRenderer that emits depth-proportional indentation for every XML tag. Attackers can provide deeply nested Markdown or AST structures to cause quadratic memory consumption and output amplification, exhausting server resources.
CVSS v4.0
Score 6.9medium
Affected software
thephpleague
commonmark
pkg:composer/thephpleague/commonmarkRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Thephpleague commonmark versions >=2.0.0 and <2.8.4 contain a denial of service vulnerability in the XmlRenderer. The renderer produces indentation for each XML tag proportional to its depth, which attackers can exploit by submitting deeply nested Markdown or AST structures. This results in quadratic memory consumption and output amplification, potentially exhausting server resources and causing denial of service.
Potential Impact
An attacker can cause a denial of service by submitting crafted deeply nested Markdown or AST input that triggers excessive memory consumption and output amplification in the XmlRenderer. This can exhaust server resources, leading to service unavailability or degraded performance.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-09-07T12:34:31.457Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a9eb72cacd9273b49a9cf7a
Added to database: 09/07/2026, 13:07:56 UTC
Last enriched: 09/15/2026, 00:01:45 UTC
Last updated: 10/07/2026, 18:48:24 UTC
Views: 73
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