# CVE-2026-115351: Mistune 3.2.1 before 3.3.0 CSS Injection via Figure Directive figwidth Option


- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 22 Oct 2026
- **Updated:** 29 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-115351, GHSA-2jmw-jfgq-rw98, GHSA-xmwc-wjpr-q378, UBUNTU-CVE-2026-115351

## What is CVE-2026-115351?

CVE-2026-115351 is a medium-severity vulnerability in lepture mistune, published on 22 Oct 2026. 

### Official description

Mistune from 3.2.1 before 3.3.0 contains a CSS injection vulnerability that allows attackers controlling markdown input to inject arbitrary style declarations via the unvalidated figwidth option of the figure directive. Attackers can append declarations like background:url() to the rendered figure style attribute, forcing victim browsers to send requests to attacker servers and leak attribute values.

Weakness: CWE-94 (Improper Control of Generation of Code)

## Which versions are affected by CVE-2026-115351?


## How do I fix CVE-2026-115351?

No fix has been published for CVE-2026-115351 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-115351 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-115351 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-115351 and fix it if it is affected.

What it is: CVE-2026-115351 is a medium-severity vulnerability in lepture mistune, published on 22 Oct 2026. 
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-115351 exists.

Affected product: lepture mistune. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-115351/ (Markdown: https://insights.sbomify.com/CVE-2026-115351/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-115351
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-115351
- OSV: https://osv.dev/vulnerability/CVE-2026-115351

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-115351/
Summaries are generated and may contain mistakes; the official description above is the record.