CVE-2026-44898 | Mistune TOC Anchor Injection XSS

Exp

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_toc_ul() builds a <ul> table-of-contents tree from a list of (level, id, text) tuples. Both the id value (used as href="#<id>") and the text value (used as the visible link label) are inserted into <a> tags via a plain Python format string — with no HTML escaping applied to either value. When heading IDs are derived from user-supplied heading text (the standard use-case for readable slug anchors), an attacker can craft a heading whose text breaks out of the href="#..." attribute context, injecting arbitrary HTML tags including <script> blocks directly into the rendered TOC. This vulnerability is fixed in 3.2.1.

Published: 2026-05-26 Last update: 2026-05-28 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-44898 is rated Exploit Available (50/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.03%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2026-44898

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-44898

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-27 — 0.03% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-44898

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.1 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.7 [email protected]

Weakness enumeration for CVE-2026-44898

GitHub Security Advisory for CVE-2026-44898

GHSA-6269-cqxg-mhhv · Severity: medium · Ecosystem: pip — Mistune TOC Anchor Injection XSS

OS Trackers for CVE-2026-44898

vendor priority summary link
debian not yet assigned CVE-2026-44898 not yet assigned priority: Debian including 1 source packages (mistune), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 5. https://security-tracker.debian.org/tracker/CVE-2026-44898
suse medium CVE-2026-44898 severity moderate: SUSE including 2 source package names (python-mistune, python3-mistune), 2 product×package rows across 1 product lines (SUSE Linux Enterprise Module for Package Hub 15 SP7): Known Not Affected 2. https://www.suse.com/security/cve/CVE-2026-44898/
ubuntu medium CVE-2026-44898 medium priority: Ubuntu including 2 source packages (mistune, mistune0), 12 status rows across 7 suites (bionic, focal, jammy, noble, questing, resolute, upstream): needs-triage 12. https://ubuntu.com/security/CVE-2026-44898

Affected software / configurations for CVE-2026-44898

Vendor Product Version Raw CPE
mistune_project mistune < 3.2.1 cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:*

References for CVE-2026-44898

cvelogic Threat Intelligence