How severe is CVE-2026-39395?

CVE-2026-39395 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2026-39395 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (15th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-39395?

CVE-2026-39395 affects Sigstore Cosign. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-39395?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-39395 have an EU (EUVD) identifier?

Yes. CVE-2026-39395 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19919.

When was CVE-2026-39395 published?

CVE-2026-39395 was published on 2026-04-07 and last updated on 2026-06-17.

CVE-2026-39395

CVE-2026-39395 is a medium-severity vulnerability in Sigstore Cosign with a CVSS 3.x base score of 4.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-754.

Key facts

Severity: Medium (CVSS 3.x base score 4.3)
EPSS exploit prediction: 0% (15th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-19919
Weakness: CWE-754
Affected product: Sigstore Cosign
Published: 2026-04-07
Last modified: 2026-06-17

Description

Cosign provides code signing and transparency for containers and binaries. Prior to 3.0.6 and 2.6.3, cosign verify-blob-attestation may erroneously report a "Verified OK" result for attestations with malformed payloads or mismatched predicate types. For old-format bundles and detached signatures, this was due to a logic flaw in the error handling of the predicate type validation. For new-format bundles, the predicate type validation was bypassed completely. This vulnerability is fixed in 3.0.6 and 2.6.3.

Frequently asked questions

What is CVE-2026-39395?: Cosign provides code signing and transparency for containers and binaries. Prior to 3.0.6 and 2.6.3, cosign verify-blob-attestation may erroneously report a "Verified OK" result for attestations with malformed payloads or mismatched predicate types. For old-format bundles and detached signatures, this was due to a logic flaw in the error handling of the predicate type validation. For new-format bundles, the predicate type validation was bypassed completely. This vulnerability is fixed in 3.0.6 and 2.6.3.
How severe is CVE-2026-39395?: CVE-2026-39395 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2026-39395 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (15th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-39395?: CVE-2026-39395 affects Sigstore Cosign. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-39395?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-39395 have an EU (EUVD) identifier?: Yes. CVE-2026-39395 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19919.
When was CVE-2026-39395 published?: CVE-2026-39395 was published on 2026-04-07 and last updated on 2026-06-17.

References

https://github.com/sigstore/cosign/security/advisories/GHSA-w6c6-c85g-mmv6

Affected products (1)

cpe:2.3:a:sigstore:cosign:*:*:*:*:*:*:*:*

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