CVE-2026-25899
Unbounded Memory Allocation via Msgpack Deserialization in Fiber v
Publication date: 2026-02-24
Last updated on: 2026-02-25
Assigner: GitHub, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| gofiber | fiber | From 3.0.0 (inc) to 3.1.0 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-789 | The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated. |
| CWE-770 | The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability exists in Fiber, a web framework written in Go, specifically in versions on the v3 branch prior to 3.1.0. It involves the `fiber_flash` cookie, which can be manipulated to cause the server to allocate an extremely large amount of memory—up to 85GB—due to unvalidated msgpack deserialization. This can be triggered by a crafted 10-character cookie value without requiring any authentication. The issue affects every GoFiber v3 endpoint regardless of whether the application uses flash messages.
How can this vulnerability impact me? :
The vulnerability can lead to a denial of service (DoS) condition by forcing the server to allocate an unbounded amount of memory, potentially up to 85GB. This can exhaust server resources, causing the application or server to crash or become unresponsive, disrupting service availability.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, upgrade the Fiber web framework to version 3.1.0 or later, as this version fixes the issue.
Since the vulnerability involves unbounded memory allocation triggered by a crafted fiber_flash cookie, consider implementing network-level protections such as filtering or blocking suspicious requests containing unusual cookie values until the upgrade is applied.