GoFiber Vulnerable to Username Enumeration via Timing Oracle in BasicAuth Default Authorizer

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

EPSS

• CVE-2026-44332: 0.52% estimated exploitation activity in the next 30 days; percentile 44.02 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The default Authorizer function in GoFiber's BasicAuth middleware uses short-circuit evaluation that skips password hash comparison for non-existent usernames. With bcrypt-hashed passwords (the primary use case), the timing difference between a valid and invalid username is approximately 1,000,000:1 (~100ms vs ~100ns), enabling reliable remote username enumeration. Vulnerable Code File: middleware/basicauth/config.go, lines 126-138 Data Flow 1. Attacker sends Authorization: Basic <base64(candidate:wrongpass) 2. BasicAuth middleware decodes credentials and calls cfg.Authorizer(user, pass, c) 3. Map lookup verifiers[user] returns ok=false for non-existent users 4. Go && short-circuit: false && verify(pass) returns immediately without calling verify() 5. For valid users, verify(pass) executes bcrypt.CompareHashAndPassword() (line 167: ~100ms at default cost 10) 6. Timing difference: ~100ns (invalid user) vs ~100ms (valid user) = 1,000,000:1 ratio Timing comparison by hash type:…

Published by the source

2 Jul 2026, 13:46 UTC

Last modified by the source

2 Jul 2026, 13:46 UTC

Source last checked

26 Oct 2026, 15:24 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-g5vh-55hw-rxm8

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# Patch Next advisory brief: CVE-2026-44332

Advisory: GoFiber Vulnerable to Username Enumeration via Timing Oracle in BasicAuth Default Authorizer
IDs: CVE-2026-44332, GHSA-g5vh-55hw-rxm8
Record: https://patchnext.com/advisories/cve-2026-44332 (revision 1, source checked 26 Oct 2026, 15:24 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/gofiber/fiber/v3 3.3.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/gofiber/fiber/v3: affected <= 3.2.0; fixed in 3.3.0

## Suggested inspection (read-only)
- Go github.com/gofiber/fiber/v3: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/gofiber/fiber/v3.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-g5vh-55hw-rxm8 (GitHub-reviewed advisory GHSA-g5vh-55hw-rxm8 lists affected ranges: Go github.com/gofiber/fiber/v3 >=0 <=3.2.0)

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