Bug 2512322 (CVE-2026-67422)

Summary: CVE-2026-67422 pymdown-extensions: Pymdown-extensions: Denial of Service via Regular Expression Vulnerability
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: abarbaro, alizardo, dschmidt, jchui, jhe, jlanda, kshier, ktsao, nboldt, oaljalju, psrna, simaishi, stcannon, teagle, yguenane
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in pymdown-extensions, a collection of extensions for the Python Markdown library. This vulnerability, known as a Regular Expression Denial of Service (ReDoS), arises from how certain inline processors handle regular expressions. An unauthenticated remote attacker can exploit this by submitting a short, untrusted Markdown line that causes the regular expression engine to perform an excessive number of calculations. This leads to unbounded CPU usage, effectively causing a denial of service for affected web applications or systems that process user-supplied Markdown.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2512405, 2512406    
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Description OSIDB Bzimport 2026-08-06 22:29:36 UTC 
pymdown-extensions is a collection of extensions for the Python Markdown library. In versions up to and including 11.0, four inline processors (caret, tilde, betterem, and magiclink) use regular expressions whose content groups can partition a run of delimiter characters in exponentially many ways, causing catastrophic backtracking. As a result, a single untrusted Markdown line under 50 bytes rendered with markdown.markdown() in each extension's default configuration drives the rendering thread into unbounded CPU usage that grows exponentially with input length, enabling an unauthenticated remote attacker who can submit Markdown to cause denial of service. The exposure is concrete for web applications that render user-supplied Markdown (comments, wikis, issue bodies, live preview), including any app using pymdownx.extra which bundles the vulnerable betterem default, as well as hosted docs/CI systems that build untrusted Markdown. The issue has been fixed in version 11.0.1.