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GHSA-wqqc-jjcq-vfxm

LowCVSS 3.1 / 10
Published Jul 31, 2026·Last modified Jul 31, 2026
Affected Components(0)

No affected components available

Description

sigstore-go fails to check signature timestamps against a signing key's validity period for self-managed long-lived keys without certificates.

Impact

To verify a bundle with a self-managed long-lived key, the key needs to be wrapped in an ExpiringKey type that implies expiration semantics:

signatureVerifier, _ := signature.LoadDefaultVerifier(publicKey)
expiredKey := root.NewExpiringKey(signatureVerifier, time.Unix(0, 0), time.Unix(1, 0))

Despite the API contract, the validator does not check the bundle signing time against the validity window. Attackers that obtain expired key materials may be able to sign bundles with those materials that are accepted despite a configured expiry date. This issue only impacts the long-lived signing key workflow, and not standard deployments involving a certificate authority.

Reproduction steps

Start from a sigstore-go checkout:

git clone https://github.com/sigstore/sigstore-go.git
cd sigstore-go
git checkout 8ca80c47ef03d26ebf174db7c296700b075b2c16

Apply the patch containing the test case and associated materials:

git apply sigstore-go-public-key-validity-test.patch

Run the test:

go test ./pkg/verify -run TestPublicKeyValidityCheckedAgainstSignedTimestamp

On vulnerable code, the test fails because verification succeeds even though the trusted ExpiringKey is not valid at the signed timestamp:

--- FAIL: TestPublicKeyValidityCheckedAgainstSignedTimestamp
    signed_entity_test.go:602:
        	Error:      	An error is expected but got nil.
Risk Scores
Base Score
3.1

The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the integrity of the data.

Threat Intelligence
2.9

Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.

EPSS
0.09%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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