Critical severity · published Feb 9, 2026
CVE-2025-66630
Fiber insecurely fallsback in utils.UUIDv4() / utils.UUID() — predictable / zero‑UUID on crypto/rand failure
9.4
CVSS
0.5%
EPSS
No
On KEV
Description
Fiber is an Express inspired web framework written in Go. Before 2.52.11, on Go versions prior to 1.24, the underlying crypto/rand implementation can return an error if secure randomness cannot be obtained. Because no error is returned by the Fiber v2 UUID functions, application code may unknowingly rely on predictable, repeated, or low-entropy identifiers in security-critical pathways. This is especially impactful because many Fiber v2 middleware components (session middleware, CSRF, rate limiting, request-ID generation, etc.) default to using utils.UUIDv4(). This vulnerability is fixed in 2.52.11.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 45% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FI
fiber · gofiber
< 2.52.11 · source: vendor, NVD
Affected product
FI
fiber
gofiber
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