# CVE-2026-53779: WebP Server Go < 0.15.0 Path Traversal via Backslash Encoding on Windows

> Unauthenticated attackers can read arbitrary files on Windows hosts by exploiting path traversal via backslash encoding in WebP Server Go.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 22 Jun 2026
- **Updated:** 24 Sep 2026
- **Also known as:** GHSA-pv77-wrq6-gq73

## What is CVE-2026-53779?

CVE-2026-53779 is a high-severity path traversal vulnerability in webp-sh webp_server_go, published on 22 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

WebP Server Go through 0.14.4 contains a path traversal vulnerability on Windows that allows unauthenticated attackers to read files outside the configured IMG_PATH directory by sending requests with percent-encoded backslashes (%5C) that bypass the path.Clean() sanitization in handler/router.go. Attackers can exploit the discrepancy between Go's forward-slash-only path normalization and Windows file system APIs that treat backslashes and forward slashes as equivalent to access arbitrary files on the host filesystem accessible to the server process.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-53779?


## How do I fix CVE-2026-53779?

No fix has been published for CVE-2026-53779 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-53779 being exploited?

There is no known exploitation of CVE-2026-53779 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53779 and fix it if it is affected.

What it is: CVE-2026-53779 is a high-severity path traversal vulnerability in webp-sh webp_server_go, published on 22 Jun 2026. 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-2026-53779 in the wild and no public exploit code.

Affected product: webp-sh webp_server_go. 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-2026-53779/ (Markdown: https://insights.sbomify.com/CVE-2026-53779/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53779
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53779
- OSV: https://osv.dev/vulnerability/CVE-2026-53779

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53779/
Summaries are generated and may contain mistakes; the official description above is the record.