CVE-2026-86432: Asymmetric Resource Consumption (Amplification) in thephpleague commonmark
Description
CVE-2026-86432 is a denial of service vulnerability in thephpleague commonmark's XmlRenderer component. Versions from 2.0.0 up to but not including 2.8.4 are affected. The vulnerability arises because the XmlRenderer emits indentation proportional to the depth of every XML tag, which can be exploited by providing deeply nested Markdown or AST structures. This causes quadratic memory consumption and output amplification, potentially 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 XmlRenderer emits indentation for each XML tag proportional to its depth. An attacker can exploit this by submitting deeply nested Markdown or AST structures, causing quadratic growth in memory usage and output size. This resource amplification can exhaust server resources, leading to denial of service conditions.
Potential Impact
The vulnerability allows an unauthenticated attacker to cause denial of service by exhausting server memory and resources through crafted deeply nested input. There is no indication of privilege escalation, data disclosure, or code execution. The impact is limited to resource exhaustion causing service disruption.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch links are provided in the available data. Until a patch is available, consider limiting input depth or size as a temporary mitigation if feasible.
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: 10/09/2026, 21:25:27 UTC
Last updated: 10/22/2026, 13:15:24 UTC
Views: 80
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