CVE-2025-66630Network attack vector

Session hijacking via silent zero-UUID fallback

Published Feb 9, 2026 · Updated Feb 9, 2026

Weak randomness in Fiber before 2.52.11 allows remote attackers to predict security-sensitive UUIDs when applications run on Go before 1.24. Fiber's utils.UUIDv4() calls googleuuid.NewRandom() but redirects errors into UUID(), whose failed rand.Read seed path returns an all-zero value. Exposure requires Go 1.23 or earlier plus a failed platform entropy source; affected middleware can then reuse session, CSRF, rate-limit, or request identifiers.

CVSS severity9.4
Critical
EPSS probability0.49%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Weak randomness in Fiber before 2.52.11 allows remote attackers to predict security-sensitive UUIDs when applications run on Go before 1.24. Fiber's utils.UUIDv4() calls googleuuid.NewRandom() but redirects errors into UUID(), whose failed rand.Read seed path returns an all-zero value. Exposure requires Go 1.23 or earlier plus a failed platform entropy source; affected middleware can then reuse session, CSRF, rate-limit, or request identifiers.

The record

CVE
CVE-2025-66630
Published
Feb 9, 2026
Updated
Feb 9, 2026
Vendor
GoFiber
Product
Fiber
Classifications
CWE-338, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.52.11

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

GoFiber · Fiberversion=< 2.52.11

Published CVSS scores

9.2GitHubCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N
9.4NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-338Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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