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VulnerabilityPublished Updated

CVE-2026-42554: gofiber fiber · Cross-site Scripting

Affects gofiber fiberSource CVE Database V5

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Not known to be exploited · CVSS 5.3 Medium : upgrade to 3.1.0 or 2.52.13 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score
5.3Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 3.1.0, 2.52.13, 2.52.12
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 11 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade fiber to 3.1.0 or 2.52.13; github.com/gofiber/fiber to 2.52.12.

Affected software

ProductAffectedFixed in
gofiberfiberAffected
  • >=3.0.0-beta.2 <3.1.0
Fixed in
  • 3.1.0
gofiberfiberAffected
  • <2.52.13
Fixed in
  • 2.52.13
Gogithub.com/gofiber/fiberpkg:golang/github.com/gofiber/fiberOther threatsAffected
  • <2.52.12
Fixed in
  • 2.52.12

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix for this vulnerability is available in Fiber versions 2.52.12 and 3.1.0. Users should upgrade to at least these versions to remediate the issue. No additional mitigation steps are indicated.

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.

References

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