CVE-2026-118694：python-markdown2 2.5.5 版因未閉合內聯連結導致拒絕服務

python-markdown2 through 2.5.5 contains a denial of service vulnerability that allows remote users to exhaust CPU by submitting Markdown with unclosed inline link destinations. Attackers can submit repeated '[a](' or '![a](' sequences, causing _find_balanced to rescan the remaining document for each link and consume quadratic CPU time.

Impact

Affected Products

The following products are affected by CVE-2026-118694 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.

Update python-markdown2 to a version that addresses the denial of service vulnerability.

• Update python-markdown2 to a fixed version.
• Avoid processing untrusted user input.
• Implement input validation for Markdown.
• Monitor CPU usage for potential DoS.

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2026-118694.

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-118694 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-118694 weaknesses.

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2026-118694 vulnerability anywhere in the article.

The following table lists the changes that have been made to the CVE-2026-118694 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

• New CVE Received by [email protected]

  十月. 28, 2026

  Action	Type	Old Value	New Value
  Added	Description		python-markdown2 through 2.5.5 contains a denial of service vulnerability that allows remote users to exhaust CPU by submitting Markdown with unclosed inline link destinations. Attackers can submit repeated '[a](' or '![a](' sequences, causing _find_balanced to rescan the remaining document for each link and consume quadratic CPU time.
  Added	CVSS V4.0		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
  Added	CVSS V3.1		AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  Added	CWE		CWE-407
  Added	Affected		New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/118xxx/CVE-2026-118694.json">CVE-2026-118694</a>
  Added	Reference		https://github.com/trentm/python-markdown2
  Added	Reference		https://github.com/trentm/python-markdown2/blob/2.5.5/lib/markdown2.py#L1478-L1492
  Added	Reference		https://github.com/trentm/python-markdown2/blob/2.5.5/lib/markdown2.py#L3029
  Added	Reference		https://github.com/trentm/python-markdown2/issues/750
  Added	Reference		https://github.com/trentm/python-markdown2/pull/751
  Added	Reference		https://www.vulncheck.com/advisories/python-markdown2-through-2.5.5-denial-of-service-via-unclosed-inline-link-destinations

EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.