CVE-2025-66630 — fiber
Fix: gofiber/fiber@eb874b6CVE-2025-66630 is a CWE-338 vulnerability in github.com/gofiber/fiber/v2. A fix is available for github.com/gofiber/fiber/v2 — see the affected versions and patch details below.
Fiber insecurely fallsback in utils.UUIDv4() / utils.UUID() — predictable / zero‑UUID on crypto/rand failure
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-66630.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
Real-World Exposure
github.com/gofiber/fiber/v2Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Fiber v2 contains an internal vendored copy of gofiber/utils, and its functions UUIDv4() and UUID() inherit the same critical weakness described in the upstream advisory. On Go versions prior to 1.24, the underlying crypto/rand implementation can return an error if secure randomness cannot be obtained. In such cases, these Fiber v2 UUID functions silently fall back to generating predictable values — the all-zero UUID 00000000-0000-0000-0000-000000000000.
On Go 1.24+, the language guarantees that crypto/rand no longer returns an error (it will block or panic instead), so this vulnerability primarily affects Fiber v2 users running Go 1.23 or earlier, which Fiber v2 officially supports.
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().
Impact includes, but is not limited to:
- Session fixation or hijacking (predictable session IDs)
- CSRF token forgery or bypass
- Authentication replay / token prediction
- Potential denial-of-service (DoS): if the zero UUID is generated, key-based structures (sessions, rate-limits, caches, CSRF stores) may collapse into a single shared key, causing overwrites, lock contention, or state corruption
- Request-ID collisions, undermining logging and trace integrity
- General compromise of confidentiality, integrity, and authorization logic relying on UUIDs for uniqueness or secrecy
All Fiber v2 versions containing the internal utils.UUIDv4() / utils.UUID() implementation are affected when running on Go <1.24. No patched Fiber v2 release currently exists.
Suggested Mitigations / Workarounds
Update to the latest version of Fiber v2.
Likelihood / Environmental Factors
It’s important to note that entropy exhaustion on modern Linux systems is extremely rare, as the kernel’s CSPRNG is resilient and non-blocking. However, entropy-source failures — where crypto/rand cannot read from its underlying provider — are significantly more likely in certain environments.
This includes containerized deployments, restricted sandboxes, misconfigured systems lacking read access to /dev/urandom or platform-equivalent sources, chrooted or jailed environments, embedded devices, or systems with non-standard or degraded randomness providers. On Go <1.24, such failures cause crypto/rand to return an error, which the Fiber v2 UUID functions currently treat as a signal to silently generate predictable UUIDs, including the zero UUID. This silent fallback is the root cause of the vulnerability.
References
-
Upstream advisory for
gofiber/utils: GHSA-m98w-cqp3-qcqr -
Source repositories:
github.com/gofiber/fibergithub.com/gofiber/utils
Credits / Reporter
Reported by @sixcolors (Fiber Maintainer / Security Team)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/gofiber/fiber/v2 | all versions | 2.52.11go get github.com/gofiber/fiber/v2@v2.52.11 |
Affected Products
fibergofiberDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/gofiber/fiber/v2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/gofiber/fiber/v2 to 2.52.11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-66630 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This vulnerability is classified as Important rather than Critical because exploitation depends on an environmental failure of the randomness source rather than a condition directly controllable by a remote attacker. The flaw does not enable immediate unauthenticated remote code execution or direct system compromise;…
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.Source: Red Hat security advisory for CVE-2025-66630 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2025-66630 in your dependencies?
Find it across Go, including transitive dependencies.