sigstore-go fails to check signature timestamps against a signing key's validity period

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

sigstore-go is a Go library for Sigstore signing and verification. Prior to 1.2.1, sigstore-go does not check a bundle signing timestamp against the validity window of an ExpiringKey wrapping a self-managed long-lived signing key without a certificate, which can allow an attacker holding expired key material to sign accepted bundles. This issue is fixed in version 1.2.1.

Source published

31 Jul 2026 21:58:14 UTC

Source modified

31 Jul 2026 23:36:13 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 3.1 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N

sigstore-go is a Go library for Sigstore signing and verification. Prior to 1.2.1, sigstore-go does not check a bundle signing timestamp against the validity window of an ExpiringKey wrapping a self-managed long-lived signing key without a certificate, which can allow an attacker holding expired key material to sign accepted bundles. This issue is fixed in version 1.2.1.

Source published

31 Jul 2026 23:17:25 UTC

Source modified

23 Oct 2026 23:10:00 UTC

Observed here

25 Oct 2026 13:17:34 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 3.1 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N

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: ```go 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: ```bash 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: ```bash git apply sigstore-go-public-key-validity-test.patch ``` Run the test: ```bash 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: ```text --- FAIL: TestPublicKeyValidityCheckedAgainstSignedTimestamp signed_entity_test.go:602: Error: An error is expected but got nil. ``` [patch]: https://github.com/user-attachments/files/28614520/sigstore-go-public-key-validity-test.patch

Source published

31 Jul 2026 21:58:39 UTC

Source modified

10 Sep 2026 03:51:12 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N

Publisher rating · LOW

sigstore-go fails to check signature timestamps against a signing key's validity period in github.com/sigstore/sigstore-go

Source published

18 Aug 2026 14:32:29 UTC

Source modified

18 Aug 2026 15:00:17 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.