CVE-2026-42554: Fiber is a web framework for Go

Routine

MEDIUM 6.1UPGRADE

CVE-2026-42554 is a medium-severity flaw (CVSS 6.1) affecting fiber. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 89%)
CISA exploited list	No
Weakness	CWE-79
Published	2026-05-11
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: gofiber

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-11 23:19 UTCPublished CVE record published
2026-10-26 18:10 UTCUpdated Record last modified

gofiber fiber UPGRADE

Affected: < 2.52.12 · >= 3.0.0 and < 3.1.0

Fixed in: 2.52.12, 3.1.0

Safe to downgrade to: a release before 3.0.0

1. Check installed version

apt-cache policy fiber || rpm -q fiber || fiber --version

2. UPGRADE to 2.52.12 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade fiber

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade fiber

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 3.0.0 (Debian / Ubuntu)

apt-cache madison fiber sudo apt install fiber=<VERSION_BEFORE_3.0.0> sudo apt-mark hold fiber

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list fiber sudo dnf downgrade fiber-<VERSION_BEFORE_3.0.0> sudo dnf versionlock add fiber

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-42554?

fiber: upgrade to 2.52.12, 3.1.0. Exact commands for each OS are on this page.

Is CVE-2026-42554 being exploited?

CVE-2026-42554 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-42554 affect?

CVE-2026-42554 affects fiber. Severity is medium (CVSS 6.1). 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 atta

How urgent is CVE-2026-42554?

Priority 29/100. Public exploit reference

Related CVEs

CVE-2026-30246 MEDIUM 6.5 UPGRADE Fiber is a web framework for Go
CVE-2026-44332 MEDIUM 5.3 UPGRADE Fiber is an Express inspired web framework written in Go
CVE-2026-45045 MEDIUM 5.3 UPGRADE Fiber is an Express inspired web framework written in Go
CVE-2026-53624 MEDIUM 4.8 UPGRADE Fiber is an Express inspired web framework written in Go

References

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