Mistune: Prior to 3.3.0, the toc plugin and TableOfContents directive generate heading IDs as predictable toc_N values
Affects mistuneSource GCVE Database
Not known to be exploited · CVSS 4.3 Medium · fixed in 1.4.0_6 : update mistune when convenient.
Data as of 26 Oct 2026, 10:12 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 1.4.0_6, 5.1.2_4
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:NExploitation evidence
Disclosed: evidence found.
CVE published 8 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade adr-viewer to 1.4.0_6; recon-ng to 5.1.2_4.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 16.04 LTSmistunepkg:deb/ubuntu/mistune?arch=source&distro=xenialOther threats | Affected
| Fixed in– |
Ubuntu 18.04 LTSmistunepkg:deb/ubuntu/mistune?arch=source&distro=bionicOther threats | Affected
| Fixed in– |
Ubuntu 20.04 LTSmistunepkg:deb/ubuntu/mistune?arch=source&distro=focalOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSmistunepkg:deb/ubuntu/mistune?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSmistunepkg:deb/ubuntu/mistune?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu 25.10mistunepkg:deb/ubuntu/mistune?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A patch is available in Mistune versions 1.4.0_6 and 5.1.2_4 that fixes the predictable ID generation issue. Users should upgrade to these or later versions to remediate the vulnerability.
Description
Mistune versions prior to 1.4.0_6 and 5.1.2_4 have a vulnerability in the toc plugin and TableOfContents directive where heading IDs are generated as predictable numeric values without slugifying the heading text. This can lead to ID collisions that may cause navigation hijacking, incorrect CSS/JS selector application, and broken accessibility associations. A patch is available to address this medium severity issue.
References
- ubuntu.com/security/CVE-2026-59930 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-59930 (opens in a new tab)
- github.com/lepture/mistune/security/advisories/GHSA-2hm2-hc3v-44h9 (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-59930 (opens in a new tab)
- github.com/lepture/mistune/commit/c4093c4742ed0d10d9332fb8edb455869b7b581b (opens in a new tab)
- github.com/lepture/mistune (opens in a new tab)
- github.com/lepture/mistune/releases/tag/v3.3.0 (opens in a new tab)
- github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-2218.yaml (opens in a new tab)