# CVE-2025-68142: PyMdown Extensions has ReDOS bug in Figure Capture extension

> Attackers can cause denial of service via ReDOS in the figure caption extension when processing malicious user content.

- **Severity:** Low 2.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Dec 2025
- **Updated:** 17 Dec 2025
- **Also known as:** DEBIAN-CVE-2025-68142, GHSA-r6h4-mm7h-8pmq, PYSEC-2026-1825, UBUNTU-CVE-2025-68142

## What is CVE-2025-68142?

CVE-2025-68142 is a low-severity denial of service vulnerability in facelessuser pymdown-extensions, published on 16 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

PyMdown Extensions is a set of extensions for the `Python-Markdown` markdown project. Versions prior to 10.16.1 have a ReDOS bug found within the figure caption extension (`pymdownx.blocks.caption`). In systems that take unchecked user content, this could cause long hanges when processing the data if a malicious payload was crafted. This issue is patched in Release 10.16.1. As a workaround, those who process unknown user content without timeouts or other safeguards in place to prevent really large, malicious content being aimed at systems may avoid the use of `pymdownx.blocks.caption` until they're able to upgrade.

Weakness: CWE-1333 (Inefficient Regular Expression Complexity)

## Which versions are affected by CVE-2025-68142?

3 open source packages ship an affected version, including pymdown-extensions. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `pymdown-extensions` | PyPI | All versions | 10.16.1 |
| `pymdown-extensions` | PyPI | All versions | 10.16.1 |
| `pymdown-extensions` | PyPI | All versions | 10.16.1 |

Products: Facelessuser Pymdown Extensions.

## How do I fix CVE-2025-68142?

Upgrade pymdown-extensions to 10.16.1 or later.

## Is CVE-2025-68142 being exploited?

There is no known exploitation of CVE-2025-68142 in the wild and no public exploit code.

## Other vulnerabilities in facelessuser pymdown-extensions

- [CVE-2023-32309](https://insights.sbomify.com/CVE-2023-32309/): Arbitrary file inclusion with the pymdowm-snippets extension (high 7.5)
- [CVE-2026-46338](https://insights.sbomify.com/CVE-2026-46338/): Regression in pymdownx.snippets reintroduces sibling-prefix path traversal bypass despite restrict_base_path (medium 4.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-68142 and fix it if it is affected.

What it is: CVE-2025-68142 is a low-severity denial of service vulnerability in facelessuser pymdown-extensions, published on 16 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-68142 in the wild and no public exploit code.

Affected packages and fixed versions:
- pymdown-extensions (PyPI): affected all versions; fixed in 10.16.1
- pymdown-extensions (PyPI): affected all versions; fixed in 10.16.1
- pymdown-extensions (PyPI): affected all versions; fixed in 10.16.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-68142/ (Markdown: https://insights.sbomify.com/CVE-2025-68142/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-68142
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-68142
- OSV: https://osv.dev/vulnerability/CVE-2025-68142

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-68142/
Summaries are generated and may contain mistakes; the official description above is the record.