PyMdown Extensions: Path traversal in the b64 extension lets <img src> read files outside base_path
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Information disclosure
- Confidentiality · integrity · availability
- Low · None · None
- Fix status
- Partial Red Hat: 3 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-22 and the CVSS impact.
Summary
PyMdown Extensions is a set of extensions for the Python-Markdown markdown project. In versions up to and including 10.21.3, the b64 extension is vulnerable to a path traversal that discloses arbitrary files: it inlines images referenced by <img src="..."> by joining the src onto the configured base_path with os.path.normpath and opening the result directly, without verifying that the resolved path stays inside base_path. As a result, an src containing ../ sequences or an absolute path reads a file outside base_path as long as it has an allowed image extension (.png, .jpg, .jpeg, .gif, .svg), and the file's contents are then base64-encoded into the rendered output, disclosing them. An application that renders untrusted Markdown with pymdownx.b64 enabled can therefore leak the contents of image-extension files readable by the process to whoever controls the Markdown or views the output, a targeted file-read bounded by the extension check. This issue has been fixed in version 11.0.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| facelessuser | pymdown-extensions | before 11.0 | 11.0 | Patch available | CNA |
| — | pymdown-extensions (PyPI) | before 11.0.0 | 11.0.0 | Patch available | GHSA-9xwg-3r6f-jcx2 |
- pymdown-extensions Vendorfacelessuser Affected before 11.0 Fixed in 11.0 Patch available CNA
- pymdown-extensions (PyPI) Vendor— Affected before 11.0.0 Fixed in 11.0.0 Patch available GHSA-9xwg-3r6f-jcx2
CPE names Threatist (inferred) · 1
Inferred from how NVD named this product before; not given by a source.
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:facelessuser:pymdown_extensions:*:*:*:*:*:*:*:* | — | — | facelessuser |
- cpe:2.3:a:facelessuser:pymdown_extensions:*:*:*:*:*:*:*:* Versions — — ·facelessuser
Remediation
- Fix · CNA pymdown-extensions (facelessuser) Fixed in 11.0
- Fix · GHSA-9xwg-3r6f-jcx2 pymdown-extensions (PyPI) Fixed in 11.0.0 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Developer Hub 1 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
| Self-service automation portal 2 | Affected | No fix yet: Fix deferred |
Not affected: 1 product
- Red Hat Hardened Images
Timeline
- 2026-10-02 Threatist record created from CVE-2026-61632
- 2026-10-03 Alias added: GHSA-9xwg-3r6f-jcx2
- 2026-10-27 Affected versions changed · Red Hat
References
Other 4
- https://github.com/facelessuser/pymdown-extensions/security/advisories/GHSA-9xwg-3r6f-jcx2
- https://github.com/facelessuser/pymdown-extensions/releases/tag/11.0
- https://github.com/facelessuser/pymdown-extensions/commit/edce35586d11a1ef78bb187bc60497fe6dbf3b64
- https://github.com/facelessuser/pymdown-extensions
More facelessuser vulnerabilities
- TI-2026-47703 pymdown-extensions: Exponential-backtracking ReDoS in caret, tilde, betterem, and magiclink inline processors CVSS 3.1HIGH 7.5
- TI-2026-36631 Soup Sieve: Regular Expression Denial of Service (ReDoS) in soupsieve Selector Parser CVSS 3.1HIGH 7.5
- TI-2026-36630 Soup Sieve: Memory Exhaustion via Large Comma-Separated Selector Lists in soupsieve CVSS 3.1HIGH 7.5
- TI-2023-15603 Arbitrary file inclusion with the pymdowm-snippets extension CVSS 3.1HIGH 7.5
- TI-2026-58861 Soup Sieve: Polynomial-time ReDoS (O(n²)) in the `IDENTIFIER` / `VALUE` selector sub-patterns CVSS 3.1MEDIUM 5.3
- TI-2026-58860 Regular expression denial of service in facelessuser soupsieve CVSS 3.1MEDIUM 5.3
Sources
- CVE-2026-61632 · CVE Program
- CVE-2026-61632 · NVD
- FIRST EPSS
- GHSA-9xwg-3r6f-jcx2 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-61632 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences