CVE-2022-23649 is a low-severity (CVSS 3.3) CWE-295 vulnerability in github.com/sigstore/cosign. A fix is available for github.com/sigstore/cosign — see the affected versions and patch details below.
Improper Certificate Validation in Cosign
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-2022-23649.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2022-23649 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/sigstore/cosignReal-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
Impact
Cosign can be manipulated to claim that an entry for a signature exists in the Rekor transparency log even if it doesn't. This requires the attacker to have pull and push permissions for the signature in OCI. This can happen with both standard signing with a keypair and "keyless signing" with Fulcio.
Signing with a keypair
<details>To reproduce this vulnerability, create a keypair and sign an image. Don't store the signature in Rekor:
$ cosign generate-key-pair
$ cosign sign --key cosign.key IMAGE
If an attacker has access to the signature in OCI, they can manipulate cosign into believing the entry was stored in Rekor even though it wasn't. To accomplish this, the attacker needs to:
- Pull the signature image
- Annotate the signature image with any valid Rekor bundle under the
dev.sigstore.cosign/bundleannotation - Push the signature image back to OCI
Verification then prints out the following:
$ cosign verify [--key] [IMAGE]
Verification for [IMAGE] --
The following checks were performed on each of these signatures:
- The cosign claims were validated
- Existence of the claims in the transparency log was verified offline
- The signatures were verified against the specified public key
- Any certificates were verified against the Fulcio roots.
[…]
The claim that Existence of the claims in the transparency log was verified offline is inaccurate since an entry for this image doesn't exist in the log.
The claim that Any certificates were verified against the Fulcio roots. is technically correct but since there were no certificates that should be explicitly called out.
"Keyless signing" with an OIDC flow
<details>To reproduce this vulnerability, sign the image with a Fulcio identity. Don't store the signature in Rekor:
$ COSIGN_EXPERIMENTAL=1 cosign sign IMAGE
[...]
IMAGE appears to be a private repository, please confirm uploading to the transparency log at "https://rekor.sigstore.dev" [Y/N]: n
Then, create a keypair and sign the image again. Store an entry for the signature in Rekor:
$ cosign generate-key-pair
$ COSIGN_EXPERIMENTAL=1 cosign sign --key cosign.key IMAGE
Enter password for private key: IMAGE appears to be a private repository, please confirm uploading to the transparency log at "https://rekor.sigstore.dev" [Y/N]: y
If an attacker has access to the signature in OCI, they can manipulate cosign into believing the entry was stored in Rekor even though it wasn't. To accomplish this, the attacker needs to:
- Pull the signature image
- Copy the rekor bundle from the second signature into the first signature under the
dev.sigstore.cosign/bundleannotation - Push the signature image back to OCI
Note: For this to work, both signatures must occur during the valid lifespan of the certificate (~20 minutes).
Verification then prints out the following:
$ cosign verify [--key] [IMAGE]
Verification for [IMAGE] --
The following checks were performed on each of these signatures:
- The cosign claims were validated
- Existence of the claims in the transparency log was verified offline
- The signatures were verified against the specified public key
- Any certificates were verified against the Fulcio roots.
[…]
The claim that Existence of the claims in the transparency log was verified offline is inaccurate since an entry for this image doesn't exist in the log.
The claim that Any certificates were verified against the Fulcio roots. is technically correct but since there were no certificates that should be explicitly called out.
Patches
The vulnerability has been patched in v1.5.2 of cosign.
The signature in the signedEntryTimestamp provided by Rekor is now compared to the signature that is being verified. If these don't match, then an error is returned. If a valid bundle is copied to a different signature, verification should fail.
Cosign output now only informs the user that certificates were verified if a certificate was in fact verified.
Workarounds
The only workaround is upgrading.
For more information
If you have any questions or comments about this advisory:
Thank you
Thank you to @mtrmac for finding and reporting this vulnerability.
Thank you to everyone who worked on fixing this:
- @nsmith5
- @znewman01
- @dlorenc
- @mattmoor
- @priyawadhwa
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/sigstore/cosign | all versions | 1.5.2go get github.com/sigstore/cosign@v1.5.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/sigstore/cosign, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/sigstore/cosign to 1.5.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-23649 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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2022-23649 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2022-23649. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2022-23649 in your dependencies?
O3 Security finds CVE-2022-23649 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.