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CVE-2026-67422— pymdown-extensions: Exponential-backtracking ReDoS in caret, tilde, betterem, and magiclink inline processors

Quick assessment

Affected
facelessuser pymdown-extensions
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

facelessuser PyMdown Extensions是facelessuser个人开发者开源的一个PythonMarkdown扩展集合。 Isaac Muse PyMdown Extensions 11.0及之前版本存在资源管理错误漏洞，该漏洞源于caret、tilde、betterem和magiclink内联处理器使用正则表达式时存在灾难性回溯问题，可能导致未经身份验证的远程攻击者通过提交Markdown内容造成拒绝服务。

CVSS 7.5 · High EPSS 0.61% · P48

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 1

VendorProduct Version RangeStatus
facelessuser pymdown-extensions < 11.0.1 affected
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I. Basic Information for CVE-2026-67422

Vulnerability Information
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Vulnerability Title
pymdown-extensions: Exponential-backtracking ReDoS in caret, tilde, betterem, and magiclink inline processors
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1333
Source: CVE Program / CVE List V5
Vulnerability Title
Isaac Muse PyMdown Extensions 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
facelessuser PyMdown Extensions是facelessuser个人开发者开源的一个PythonMarkdown扩展集合。 Isaac Muse PyMdown Extensions 11.0及之前版本存在资源管理错误漏洞，该漏洞源于caret、tilde、betterem和magiclink内联处理器使用正则表达式时存在灾难性回溯问题，可能导致未经身份验证的远程攻击者通过提交Markdown内容造成拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
facelessuser pymdown-extensions < 11.0.1 -

II. Public POCs for CVE-2026-67422

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Qwen3.6-35B-A3B · 11615 chars
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III. Intelligence Information for CVE-2026-67422

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Patches & Fixes for CVE-2026-67422 (1)

Vendor Advisories for CVE-2026-67422 (1)

IV. Related Vulnerabilities

Same product: pymdown-extensions
Same vendor: facelessuser
Same weakness: CWE-1333