# CVE-2026-111139: NetSurf libnsbmp through 0.1.7 Out-of-Bounds Read via bmp_decode_mask

> Attackers can cause a crash or read memory by supplying crafted ICO files to applications using the NetSurf libnsbmp library.

- **Severity:** Medium 6.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 15 Oct 2026
- **Updated:** 26 Oct 2026
- **Also known as:** GHSA-j4g8-9gm4-w4v9, UBUNTU-CVE-2026-111139

## What is CVE-2026-111139?

CVE-2026-111139 is a medium-severity memory corruption vulnerability in NetSurf libnsbmp, published on 15 Oct 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

NetSurf libnsbmp through 0.1.7 contains an out-of-bounds read vulnerability in bmp_decode_mask() that allows attackers to read one byte past the image buffer by supplying crafted ICO files. Attackers can provide an ICO whose inner bitmap width is not a multiple of 8, causing a heap over-read that can crash applications calling bmp_decode().

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-111139?


## How do I fix CVE-2026-111139?

No fix has been published for CVE-2026-111139 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-111139 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-111139 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-111139 and fix it if it is affected.

What it is: CVE-2026-111139 is a medium-severity memory corruption vulnerability in NetSurf libnsbmp, published on 15 Oct 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-111139 exists.

Affected product: NetSurf libnsbmp. 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-2026-111139/ (Markdown: https://insights.sbomify.com/CVE-2026-111139/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-111139
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-111139
- OSV: https://osv.dev/vulnerability/CVE-2026-111139

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-111139/
Summaries are generated and may contain mistakes; the official description above is the record.