CVE-2025-6224 is a medium-severity (CVSS 6.5) CWE-312 vulnerability in github.com/juju/utils/v4/cert. A fix is available for github.com/juju/utils/v4/cert — see the affected versions and patch details below.
Key leakage in juju/utils certificates
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-6224.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/juju/utils/v4/certReal-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
Summary
Certs generated by v4 contain their private key.
Details
Background
Recently, I encountered an API in Go that’s easy to misuse: sha512.Sum384 and sha512.New384().Sum look very similar and behave very differently. https://go.dev/play/p/kDCqqoYk84k demonstrates this. I want to discuss extending static analysis to detect this case with the go community, but before I do that, I want to make a best-effort pass at open-source projects to fix the existing bugs. I figured that if there were any vulnerabilities out there, they would be easy to find once that discussion begins, so it’s better to address them early.
This work is a hobby project and has no affiliation with my employer, so I may be slow to respond due to existing commitments.
PoC
https://go.dev/play/p/vSW0U3Hq4qk
Impact
This code (cert.NewLeaf) generates certs with the SubjectKeyId set to sha512.New384().Sum(/* private */ key).
If a cert which was generated by cert.NewLeaf is transferred over the network in plaintext, as is often the case in TLS handshakes, an attacker listening on that network may sniff the cert and trivially extract the private key from it. This applies to client and server TLS certs generated by vulnerable versions of this library.
Getting the server cert and its key would only require performing a TLS handshake (with a matching SNI) with the server. At that point, the attacker could impersonate the server.
Similarly, getting the client cert and its key would require getting the client to perform a TLS handshake against an attacker-controlled server. At that point, an attacker could impersonate the client.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/juju/utils/v4/cert | all versions | 4.0.4go get github.com/juju/utils/v4/cert@v4.0.4 |
Affected Products
juju\/utilscanonicalDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/juju/utils/v4/cert, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/juju/utils/v4/cert to 4.0.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-6224 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2025-6224 in your dependencies?
Find it across Go, including transitive dependencies.