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CVE-2026-42554— Fiber: XSS in AutoFormat Content Negotiation

Quick assessment

Affected
gofiber fiber
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Fiber是Fiber开源的一款使用Go语言编写的开源Web框架。 Fiber 2.52.12之前版本和3.1.0之前版本存在跨站脚本漏洞，该漏洞源于跨站脚本，可能导致远程攻击者通过提供Accept: text/html在任意请求中注入任意HTML/JavaScript，当处理程序将攻击者影响的数据传递给AutoFormat()功能时触发。

AI Predicted 6.1 Difficulty: Easy EPSS 0.31% · P21

Affected Version Matrix 2

VendorProduct Version RangeStatus
gofiber fiber < 2.52.13 affected
>= 3.0.0-beta.2, < 3.1.0 affected
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I. Basic Information for CVE-2026-42554

Vulnerability Information
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Vulnerability Title
Fiber: XSS in AutoFormat Content Negotiation
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5
Vulnerability Title
Fiber 跨站脚本漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Fiber是Fiber开源的一款使用Go语言编写的开源Web框架。 Fiber 2.52.12之前版本和3.1.0之前版本存在跨站脚本漏洞，该漏洞源于跨站脚本，可能导致远程攻击者通过提供Accept: text/html在任意请求中注入任意HTML/JavaScript，当处理程序将攻击者影响的数据传递给AutoFormat()功能时触发。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
gofiber fiber < 2.52.13 -

II. Public POCs for CVE-2026-42554

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III. Intelligence Information for CVE-2026-42554

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Vendor Advisories for CVE-2026-42554 (1)

IV. Related Vulnerabilities

Same product: fiber
Same vendor: gofiber
Same weakness: CWE-79

V. Comments for CVE-2026-42554

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