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

Quick assessment

Affected
gofiber fiber
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Fiber是Fiber开源的一款使用Go语言编写的开源Web框架。 Fiber 3.1.0之前版本存在安全漏洞，该漏洞源于fiber_flash cookie可通过未经验证的msgpack反序列化触发大量内存分配，可能导致拒绝服务攻击。

CVSS 7.5 · High EPSS 0.63% · P48

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-25899

Vulnerability Information
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Vulnerability Title
Fiber is Vulnerable to Denial of Service via Flash Cookie Unbounded Allocation
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未经控制的内存分配
Source: CVE Program / CVE List V5
Vulnerability Title
Fiber 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Fiber是Fiber开源的一款使用Go语言编写的开源Web框架。 Fiber 3.1.0之前版本存在安全漏洞，该漏洞源于fiber_flash cookie可通过未经验证的msgpack反序列化触发大量内存分配，可能导致拒绝服务攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
gofiber fiber >= 3.0.0, < 3.1.0 -

II. Public POCs for CVE-2026-25899

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III. Intelligence Information for CVE-2026-25899

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Vendor Advisories for CVE-2026-25899 (1)

Same Patch Batch · gofiber · 2026-02-24 · 3 CVEs total

CVE-2026-25882 Fiber has a Denial of Service Vulnerability via Route Parameter Overflow
CVE-2026-25891 Fiber has an Arbitrary File Read in Static Middleware on Windows

IV. Related Vulnerabilities

Same product: fiber
Same vendor: gofiber
Same weakness: CWE-789

V. Comments for CVE-2026-25899

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