EUVD-2026-72386
GHSA-8h74-w38m-j62j
Severity by source
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:X/V:X/RE:X/U:X
Network-delivered DoS with no auth or interaction required once AttributesExtension is active; AC:L because crafting distinct attribute names is trivial and requires no special knowledge.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
Lifecycle Timeline
5DescriptionCVE.org
commonmark versions from 1.5.0 before 2.10.0 contain a denial of service vulnerability in the AttributesExtension when processing distinctly-named attributes. Attackers can submit Markdown with numerous distinct attribute names to cause quadratic-time attribute merging and filtering, consuming disproportionate CPU resources and preventing legitimate requests from completing.
AnalysisAI
Quadratic CPU exhaustion in league/commonmark's optional AttributesExtension (versions 1.5.0 through 2.9.2) allows unauthenticated remote attackers to perform denial of service against PHP applications that explicitly register this extension. By submitting Markdown containing many distinctly-named attributes targeting a common block, an attacker triggers O(n²) attribute merging and filtering loops; a 256 KB payload consumes over 20 seconds of PHP CPU time per conversion request. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires that the target application explicitly registers AttributesExtension on its league/commonmark Environment instance - this is an opt-in configuration not present in CommonMarkConverter, GithubFlavoredMarkdownConverter, or GithubFlavoredMarkdownExtension; applications using only these built-in converters are completely unaffected. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 4.0 score of 8.7 (AV:N/AC:L/AT:N/PR:N/UI:N/VA:H) is technically accurate for a fully exposed deployment but overstates risk for the majority of installations: AttributesExtension is opt-in and absent from all built-in converter classes, so most commonmark deployments are entirely unaffected. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade league/commonmark to version 2.10.0 or later, which contains the complete fix at commit f27eb720972490b5af4dbb635ad8634529faf9f2; run `composer require league/commonmark:^2.10.0` to update and pin to the patched range. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, audit all PHP deployments to identify instances of league/commonmark versions 1.5.0 through 2.9.2 and confirm whether the AttributesExtension is explicitly registered in application configuration (search for registerExtension() calls in code and configuration). …
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External POC / Exploit Code
Leaving vuln.today