CVE-2025-66565Network attack vector

Predictable identifiers via silent randomness failure

Published Dec 9, 2025 · Updated Dec 9, 2025

Cryptographic failure in GoFiber Fiber Utils 1.1.0 and earlier and v2 before 2.0.0-rc.4 allows attackers to obtain predictable UUIDs. UUIDv4 falls back to UUID after uuid.NewRandom fails, while UUID ignores crypto/rand seeding failure and silently returns an all-zero identifier. The behavior requires Go before 1.24 and failed system randomness; security-critical use exposes sessions or tokens to collision, replay, or hijacking.

CVSS severity9.2
Critical
EPSS probability0.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cryptographic failure in GoFiber Fiber Utils 1.1.0 and earlier and v2 before 2.0.0-rc.4 allows attackers to obtain predictable UUIDs. UUIDv4 falls back to UUID after uuid.NewRandom fails, while UUID ignores crypto/rand seeding failure and silently returns an all-zero identifier. The behavior requires Go before 1.24 and failed system randomness; security-critical use exposes sessions or tokens to collision, replay, or hijacking.

The record

CVE
CVE-2025-66565
Published
Dec 9, 2025
Updated
Dec 9, 2025
Vendor
GoFiber
Product
Fiber Utils
Classifications
CWE-252, CWE-338, CWE-331, T1550.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 9, 2025CVE publishedPublication date reported by the CVE source.
  2. Dec 9, 2025Record 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=github.com/gofiber/utils <= 1.2.0
  2. Affected versionversion=github.com/gofiber/utils/v2 < 2.0.0-rc.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

GoFiber · Fiber Utilsversion=github.com/gofiber/utils <= 1.2.0; version=github.com/gofiber/utils/v2 < 2.0.0-rc.4

Published CVSS scores

9.2GitHubCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N

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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-252Unchecked Return Value
CWE-338Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)
CWE-331Insufficient Entropy
T1550.004Web Session Cookie

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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