Path Traversal in mistune (CVE-2026-59924)
Summary
Path traversal in mistune (CVE-2026-59924). Confidential information can be exposed externally. Exploitable via Include. Mitigation: upgrade to 3.3.0 or later.
Original description
The description as published by the source.
Summary
A path traversal issue exists in mistune's Include directive when markdown files are processed using md.read(). A crafted include path can cause files outside the intended markdown directory to be accessed.
Details
The issue occurs in the Include.parse() method where user-supplied paths are joined and normalized without verifying that the resulting path remains within an expected directory.
relpath = self.parse_title(m)
dest = os.path.join(os.path.dirname(source_file), relpath)
dest = os.path.normpath(dest)
Because the final path is not restricted to a trusted base directory, path traversal sequences such as ../ may reference files outside the intended location.
Proof of Concept
Create a markdown file:
.. include:: ../../../example.txt
Process it using:
import mistune
from mistune.directives import RSTDirective, Include
md = mistune.create_markdown(
plugins=[RSTDirective([Include()])]
)
result, state = md.read("test.md")
print(result)
Impact
Applications that process untrusted markdown files with the Include directive enabled may allow unintended file access. The impact depends on how the feature is used and what files are accessible to the running process.
Recommended Fix
Validate the resolved path and ensure it remains within an allowed directory before opening the file.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-59924 has been found in mistune.
Attackers can target a specific entry point like Include over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 5.9/10.
What to do: upgrade mistune to 3.3.0 or later.
If unsure, ask your IT team or search "mistune CVE-2026-59924" on the vendor's site.
CVE-2026-59924 (mistune) — CWE-22 / CVSS v3 5.9
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: Include
Patched: 3.3.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Path traversal (CWE-22) exists in mistune. Attackers reach the vulnerable code path via Include without authentication.
Check the vendor advisory for the affected versions of mistune. Attack surface: Include.
Severity: Medium (CVSS 5.9/10). Confidential information can be exposed externally.
Update to 3.3.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'mistune' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'mistune' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
mistuneを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade mistune to 3.3.0ステージング環境で 3.3.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Ubuntu UBUNTU-CVE-2026-59924 mistune
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com