CVE-2026-25899 HIGH

CVE-2026-25899: Fiber is Vulnerable to Denial of Service via Flash Cookie Unbounded Allocation

Vendor Gofiber
Product fiber
Weakness CWE-789
Published February 24, 2026
Last update February 24, 2026

CVSS base score

7.5/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality None
Integrity None

CVSS vector

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

What the vulnerability does

01Description

Fiber is an Express inspired web framework written in Go. In versions on the v3 branch prior to 3.1.0, the use of the `fiber_flash` cookie can force an unbounded allocation on any server. A crafted 10-character cookie value triggers an attempt to allocate up to 85GB of memory via unvalidated msgpack deserialization. No authentication is required. Every GoFiber v3 endpoint is affected regardless of whether the application uses flash messages. Version 3.1.0 fixes the issue.

Key dates

02Disclosure timeline

February 24, 2026 CVE published
February 24, 2026 Record updated