Fiber: XSS in AutoFormat Content Negotiation_CVE-2026-42554

5.3 / 10

MEDIUM

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

Description

Fiber is a web framework for Go. Prior to 2.52.12 and 3.1.0, Cross-Site Scripting vulnerability in Go Fiber allows a remote attacker to inject arbitrary HTML/JavaScript by supplying Accept: text/html on any request whose handler passes attacker-influenced data to the AutoFormat() feature. The developer opts into content negotiation by calling AutoFormat(), but does not opt into raw HTML emission for a particular request; Fiber chooses that branch from attacker-controlled Accept. The html branch is the sole outlier in a method whose name (AutoFormat) and symmetrical structure actively telegraph "safe, format-agnostic reply." This vulnerability is fixed in 2.52.12 and 3.1.0.

Basic Information

ID CVE-2026-42554

Source GitHub_M

Published May 11, 2026 at 21:47

Affected Product

Vendor gofiber

Product fiber

Version < 2.52.13

Affected Versions gofiber fiber < 2.52.13
gofiber fiber >= 3.0.0-beta.2, < 3.1.0

CWE Classification

CWE-79

References

github.com /gofiber/fiber/security/advisories/GHSA-qjv7-627w-8qjv

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