Fiber's cache middleware default key generator ignores query string, causing response mix-up across distinct query parameters

Exploitation

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

CVSS

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

EPSS

• CVE-2026-30246: 0.25% estimated exploitation activity in the next 30 days; percentile 16.58 (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 Fiber cache middleware's default key generator uses only c.Path() and does not include the query string. As a result, requests like /?id=1 and /?id=2 can map to the same cache key and share the same cached response. This can cause response mix-up (cache poisoning-like behavior) for endpoints where response content depends on query parameters. Details Default configuration in cache middleware: - KeyGenerator: func(c fiber.Ctx) string { return utils.CopyString(c.Path()) } References: - https://github.com/gofiber/fiber/blob/main/middleware/cache/config.go#L90-L92 - https://github.com/gofiber/fiber/blob/main/middleware/cache/cachetest.go#L599-L621 The existing test demonstrates that when handler output depends on query parameter id, a second request with a different query still returns the first cached response (cache hit), confirming query is not part of the default cache key. PoC Minimal PoC: Reproduction: 1. GET /?id=1 - Cache miss - Response body: 1 2. GET /?id=2 - Cache hit…

Published by the source

28 Apr 2026, 22:28 UTC

Last modified by the source

8 May 2026, 13:42 UTC

Source last checked

26 Oct 2026, 15:20 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-35hp-hqmv-8qg8

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# Patch Next advisory brief: CVE-2026-30246

Advisory: Fiber's cache middleware default key generator ignores query string, causing response mix-up across distinct query parameters
IDs: CVE-2026-30246, GHSA-35hp-hqmv-8qg8
Record: https://patchnext.com/advisories/cve-2026-30246 (revision 1, source checked 26 Oct 2026, 15:20 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
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 3.2.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/gofiber/fiber/v3: affected <= 3.1.0; fixed in 3.2.0

## 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-35hp-hqmv-8qg8 (GitHub-reviewed advisory GHSA-35hp-hqmv-8qg8 lists affected ranges: Go github.com/gofiber/fiber/v3 >=0 <=3.1.0)

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