Answer in brief
CVE-2026-39395 records a Medium severity (CVSS 4.3) vulnerability in Cosign's verify-blob-attestation reports false positive when payload parsing fails in github.com/sigstore/cosign. The current sources do not mark it as known exploited. The current feed maps github.com/sigstore/cosign (go), github.com/sigstore/cosign (go), github.com/sigstore/cosign (go), github.com/sigstore/cosign (go) and additional mapped packages. Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 4.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps github.com/sigstore/cosign (go), github.com/sigstore/cosign (go), github.com/sigstore/cosign (go), github.com/sigstore/cosign (go) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| github.com/sigstore/cosigngo | >=3.0.0 <3.0.6 | 3.0.6 |
| github.com/sigstore/cosigngo | >=0 <2.6.3 | 2.6.3 |
| github.com/sigstore/cosigngo | >=0 | Not reported |
| github.com/sigstore/cosigngo | <=1.13.6 | Not reported |
| github.com/sigstore/cosign/v2go | >=0 <2.6.3 | 2.6.3 |
| github.com/sigstore/cosign/v2go | <2.6.3 | 2.6.3 |
| github.com/sigstore/cosign/v3go | >=3.0.0 <3.0.6 | 3.0.6 |
| github.com/sigstore/cosign/v3go | >=3.0.0,<3.0.6 | 3.0.6 |
Published upstream
Apr 8, 2026
Evidence: source:ghsa:source_dates:source-dates:recordSource modified
Nov 12, 2026
Evidence: source:ghsa:source_dates:source-dates:recordFirst seen by HOL
Aug 8, 2026
## Description `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. ## Impact When `cosign verify-blob-attestation` is used without `--check-claims` set to `true`, an attestation that has a valid signature but a malformed or unparsable payload would be incorrectly validated. Additionally, systems relying on `--type <predicate type>` to reject attestations with mismatched types would be lead to trust the unexpected attestation type. ## Patches v3.0.6, v2.6.3 ## Workarounds Always set `--check-claims=true` for attestation verification.
Quoted source text, attributed separately from HOL analysis.