CVE-2025-54801: Fiber Susceptible to Crash via `BodyParser` Due to Unvalidated Large Slice Index in Decoder

Vulnerability summary

CVE-2025-54801 is a high (CVSS 8.7) vulnerability in gofiber fiber. EPSS estimates a 0.37% chance of exploitation in the next 30 days, higher than 29.9% of scored vulnerabilities.

Timeline

1. 05-08-2025
   PublishedVulnerability first disclosed.
2. 07-08-2025
   Last modifiedVulnerability information updated.

Description

Fiber is an Express inspired web framework written in Go. In versions 2.52.8 and below, when using Fiber's Ctx.BodyParser to parse form data containing a large numeric key that represents a slice index (e.g., test.18446744073704), the application crashes due to an out-of-bounds slice allocation in the underlying schema decoder. The root cause is that the decoder attempts to allocate a slice of length idx + 1 without validating whether the index is within a safe or reasonable range. If the idx is excessively large, this leads to an integer overflow or memory exhaustion, causing a panic or crash. This is fixed in version 2.52.9.

• CWE-789Memory Allocation with Excessive Size ValueThe 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.