CVE-2023-22484 in cmark-gfm
Summary
by MITRE • 01/24/2023
cmark-gfm is GitHub's fork of cmark, a CommonMark parsing and rendering library and program in C. Versions prior to 0.29.0.gfm.7 are subject to a polynomial time complexity issue in cmark-gfm that may lead to unbounded resource exhaustion and subsequent denial of service. This vulnerability has been patched in 0.29.0.gfm.7.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 03/04/2025
The cmark-gfm library represents a critical parsing and rendering component used extensively across GitHub's infrastructure and third-party applications for processing markdown content. This library serves as the foundation for markdown parsing in numerous development environments, documentation systems, and content management platforms. The vulnerability CVE-2023-22484 specifically targets the time complexity characteristics of the parsing algorithm, creating a significant security risk that affects all versions prior to the patched release 0.29.0.gfm.7. The flaw manifests within the core parsing logic that processes CommonMark compliant markdown documents, making it a fundamental issue that impacts the reliability and availability of systems relying on this library.
The technical implementation of this vulnerability stems from an algorithmic inefficiency in how cmark-gfm handles certain markdown constructs during the parsing phase. When processing malformed or specially crafted markdown input, the parser exhibits polynomial time complexity behavior that can escalate to unbounded resource consumption. This occurs because the parsing algorithm fails to properly bound the computational resources required for processing specific patterns of nested elements, nested lists, or complex markdown structures. The vulnerability operates at the level of the parsing engine itself, making it particularly dangerous as it can be exploited through user-provided content without requiring special privileges or authentication. The issue falls under the CWE-778 vulnerability category, which specifically addresses insufficient logging or monitoring of resource consumption, though it manifests more precisely as a computational complexity attack vector.
The operational impact of this vulnerability extends far beyond simple denial of service conditions, as it can effectively render systems unusable by consuming all available CPU and memory resources. When exploited, the vulnerability allows attackers to craft malicious markdown documents that cause the parser to enter into computationally expensive processing loops, potentially leading to system crashes, application hangs, or complete service outages. This makes the vulnerability particularly dangerous in environments where markdown processing is performed on untrusted input, such as user-generated content platforms, collaborative development environments, or documentation systems. The attack surface is broad given cmark-gfm's widespread adoption, potentially affecting thousands of applications and services that depend on this parsing library for handling markdown content, from static site generators to collaborative editing platforms and continuous integration systems.
Organizations should immediately prioritize upgrading to version 0.29.0.gfm.7 or later to mitigate this vulnerability, as no effective workarounds exist for the underlying algorithmic issue. The patch addresses the root cause by implementing proper bounds checking and resource limiting within the parsing algorithm, ensuring that even maliciously crafted input cannot cause unbounded resource consumption. System administrators should also consider implementing input validation and rate limiting mechanisms as additional defensive measures, though these should be viewed as supplementary protections rather than primary solutions. From an ATT&CK perspective, this vulnerability maps to the T1499.004 technique related to network denial of service, and the T1070.004 technique involving the use of system logs for monitoring and detection. Regular security assessments should include verification of cmark-gfm versions across all dependent systems, and organizations should establish monitoring protocols to detect unusual resource consumption patterns that might indicate exploitation attempts. The vulnerability highlights the importance of proper algorithmic complexity analysis in security-critical components and demonstrates how seemingly benign parsing operations can become significant attack vectors when not properly bounded.