# CVE-2026-59959: SAIL: WebP decoder division by zero through malformed animated canvas metadata


- **Severity:** Medium 4.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 28 Oct 2026
- **Updated:** 29 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-59959, GHSA-5g8g-g347-84m8

## What is CVE-2026-59959?

CVE-2026-59959 is a medium-severity vulnerability in HappySeaFox sail, published on 28 Oct 2026. 

### Official description

SAIL is a cross-platform library for loading and saving images with support for animation, metadata, and ICC profiles. Prior to version 1.0.2, the built-in WebP decoder can crash during loader initialization when processing a malformed animated WebP file with inconsistent container or `ANMF` frame metadata. In `sail_codec_load_init_v8_webp()` in `src/sail-codecs/webp/webp.c`, `WebPDemuxGetI` with `WEBP_FF_CANVAS_WIDTH` can return a zero `image_local->width`, which is then used as a divisor when calculating `bytes_per_pixel` from the image row size. The division happens before frame decoding and before generic image skeleton validation in `src/sail/sail_advanced.c`, causing an arithmetic fault and process termination. Applications accepting untrusted WebP images can consequently suffer denial of service; builds must include the affected WebP codec. This issue is fixed in version 1.0.2.

Weakness: CWE-369 (Divide By Zero)

## Which versions are affected by CVE-2026-59959?


## How do I fix CVE-2026-59959?

Upgrade to a fixed version.

## Is CVE-2026-59959 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59959 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-59959 and fix it if it is affected.

What it is: CVE-2026-59959 is a medium-severity vulnerability in HappySeaFox sail, published on 28 Oct 2026. 
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59959 exists.

Affected product: HappySeaFox sail. 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-2026-59959/ (Markdown: https://insights.sbomify.com/CVE-2026-59959/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-59959
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-59959
- OSV: https://osv.dev/vulnerability/CVE-2026-59959

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-59959/
Summaries are generated and may contain mistakes; the official description above is the record.