# CVE-2026-25899: GO-2026-4534 - Fiber is Vulnerable to Denial of Service via Flash Cookie Unbounded Allocation in github.com/gofiber/fiber/v3

Source: https://junglewise.ai/threats/cve-2026-25899-fiber-is-vulnerable-to-denial-of-service-via-flash-cookie  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-02-26  
License: CC BY 4.0 with a link back

CVE-2026-25899 · Severity: low · CVSS 3.1 · Published 2026-02-26

Fiber is Vulnerable to Denial of Service via Flash Cookie Unbounded Allocation in github.com/gofiber/fiber/v3

Technologies: [github.com/gofiber/fiber/v3 (Go)](https://junglewise.ai/threats/technologies/github-com-gofiber-fiber-v3). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-25899 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-25899 being exploited in the wild.

**How severe is CVE-2026-25899?** Low severity, with a CVSS score of 3.1, published 26 February 2026.

**Which products and versions are affected?** github.com/gofiber/fiber/v3 (Go) SEMVER:introduced=0,fixed=3.1.0.

**Is there a fix for CVE-2026-25899?** Yes. github.com/gofiber/fiber/v3 (Go): upgrade to 3.1.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2026-25899?** Check whether you run github.com/gofiber/fiber/v3 (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/gofiber/fiber/v3 (Go): upgrade to 3.1.0 or later

  ```sh
  go get github.com/gofiber/fiber/v3@v3.1.0
  ```


## Affected products

- github.com/gofiber/fiber/v3 (Go) SEMVER:introduced=0,fixed=3.1.0

## Identifiers

- CVE-2026-25899
- GHSA-2mr3-m5q5-wgp6
- GO-2026-4534

## Related threats

- [Gofiber Fiber HSTS header omission in helmet middleware](https://junglewise.ai/threats/cve-2026-53624-gofiber-fiber-hsts-header-omission-in-helmet-middleware)
- [Gofiber Fiber IP spoofing in BalancerForward proxy helper](https://junglewise.ai/threats/cve-2026-45045-gofiber-fiber-ip-spoofing-in-balancerforward-proxy-helper)
- [Gofiber Fiber username enumeration in BasicAuth middleware](https://junglewise.ai/threats/cve-2026-44332-gofiber-fiber-username-enumeration-in-basicauth-middleware)
- [Go Fiber XSS in AutoFormat content negotiation](https://junglewise.ai/threats/cve-2026-42554-go-fiber-xss-in-autoformat-content-negotiation)
- [Gofiber Fiber response mix-up in cache middleware](https://junglewise.ai/threats/cve-2026-30246-gofiber-fiber-response-mix-up-in-cache-middleware)