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Sigstore Java has a vulnerability with bundle verification of integratedTime

Low severity GitHub Reviewed Published May 26, 2026 in sigstore/sigstore-java

Package

maven dev.sigstore:sigstore-java (Maven)

Affected versions

= 2.0.0

Patched versions

2.1.0

Description

Summary

Regression: Verification of integratedTime from Rekor V1 Log Entry against Fuclio Certificate validity was missing

Details

  • PR #1008 erroneously removed verification of the integrated (Rekor entry) time) against the Fulcio certificate.
  • PR #1185 re-added this verification with enhancements that adhere to the Sigstore verification spec.
  • old sigstore-conformance test for this check was built incorrectly

PoC

A new bundle was added to sigstore-conformance to test this: sigstore-java:2.0.0 can be tested against it and shown to be unexpectedly passing
Verify this bundle against a.txt

$ git clone git@github.com:sigstore/sigstore-java
$ git checkout v2.0.0
$ ./gradlew :sigstore-cli:build
$ tar -xf sigstore-cli/build/distributions/sigstore-cli-*-SNAPSHOT.tar --strip-components 1
$ ./bin/sigstore-cli verify --bundle=bundle.sigstore.json a.txt
# expect error but none

Impact

This vulnerability impacts only users verifying bundles with dev.sigstore:sigstore-java:2.0.0. Older versions are not affected, it is fixed in dev.sigstore:sigstore-java:2.1.0

A malicious actor may exploit this if they were able to access a users system and exfiltrate the temporary private key used during signing and then reuse an old fulcio certificate later without requiring direct access to the user's credentials.

Users may protect themselves by re-verifying their artifacts using the newest sigstore-java or another current sigstore client. Transparency logs may also be audited for unauthorized signatures for a suspected reused identity.

References

@loosebazooka loosebazooka published to sigstore/sigstore-java May 26, 2026
Published to the GitHub Advisory Database Jun 30, 2026
Reviewed Jun 30, 2026

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
Low
Privileges required
High
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:L/PR:H/UI:R/S:U/C:N/I:L/A:N

EPSS score

Weaknesses

Improper Verification of Cryptographic Signature

The product does not verify, or incorrectly verifies, the cryptographic signature for data. Learn more on MITRE.

CVE ID

CVE-2026-48791

GHSA ID

GHSA-qqw8-7c2r-jxch

Source code

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