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

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-22 · updated 2026-10-25
Weakness: CWE-22

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.

Affected products

webp-sh webp_server_go: before 0.15.0 — fixed in 0.15.0

How to fix

Upgrade to a fixed version: webp-sh webp_server_go 0.15.0. Check the vendor advisory for mitigations.

References

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