What is the CVSS score of CVE-2026-48791?

CVE-2026-48791 has a CVSS 3.1 base score of 2.0 (Low). CVSS vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:R/S:U/C:N/I:L/A:N. EPSS exploitation probability: 0.1%.

Is there a public PoC exploit available for CVE-2026-48791?

Yes, a public proof-of-concept exploit is available for CVE-2026-48791. Prioritise patching immediately. EPSS: 0.1%.

Is there a patch available for CVE-2026-48791?

Yes, a patch is available for CVE-2026-48791. Update the affected software to the latest version immediately.

sigstore-java CVE-2026-48791

LOW

Improper Verification of Cryptographic Signature (CWE-347)

2026-06-30 https://github.com/sigstore/sigstore-java

GHSA-qqw8-7c2r-jxch

Authentication Bypass Java Jwt Attack

2.0

CVSS 3.1 · Vendor: https://github.com/sigstore/sigstore-java

Severity by source

Vendor (https://github.com/sigstore/sigstore-java) PRIMARY

2.0 LOW

AV:L/AC:L/PR:H/UI:R/S:U/C:N/I:L/A:N

vuln.today AI

2.0 LOW

Exploitation demands prior local compromise and key exfiltration (PR:H, AV:L); integrity impact is limited to verification bypass with no scope change or confidentiality loss.

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

4.0 AV:L/AC:L/AT:N/PR:H/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (https://github.com/sigstore/sigstore-java).

CVSS VectorVendor: https://github.com/sigstore/sigstore-java

Attack Vector

Local

Attack Complexity

Low

Privileges Required

High

User Interaction

Required

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

None

Lifecycle Timeline

Analysis Generated

Jun 30, 2026 - 18:51 vuln.today

Blast Radius

ecosystem impact

† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth

3 maven packages depend on dev.sigstore:sigstore-java (2 direct, 1 indirect)

Ecosystem-wide dependent count for version 2.0.0.

DescriptionCVE.org

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.

AnalysisAI

Certificate timestamp validation bypass in sigstore-java 2.0.0 allows an attacker who has already exfiltrated an ephemeral Sigstore signing key to reuse an expired Fulcio certificate, causing bundle verification to succeed when it should fail. PR #1008 erroneously removed the check that bounds a Rekor V1 log entry's integratedTime against the Fulcio certificate's validity window, a regression only present in the 2.0.0 release and fixed in 2.1.0. No public exploit identified at time of analysis beyond the vendor-provided proof-of-concept test bundle in sigstore-conformance; CVSS base score of 2.0 reflects the extremely narrow, high-privilege, local-only attack conditions required.

Technical ContextAI

sigstore-java (Maven artifact pkg:maven/dev.sigstore:sigstore-java) is the Java client implementation of the Sigstore software supply-chain security framework, which pairs Fulcio (a short-lived certificate authority) with Rekor (an append-only transparency log) to bind signed artifacts to a specific identity at a specific point in time. The critical invariant Sigstore enforces is that the integratedTime field embedded in a Rekor V1 log entry must fall within the certificate's notBefore/notAfter validity window, proving the signing event occurred while the certificate was live. CWE-347 (Improper Verification of Cryptographic Signature) captures the root cause: by omitting this temporal cross-check, the library accepts bundles whose Rekor timestamps fall outside the certificate's validity period - undermining the time-binding guarantee that is central to Sigstore's security model. The fix in PR #1185 re-implements the check in conformance with the Sigstore verification specification.

RemediationAI

Upgrade dev.sigstore:sigstore-java to version 2.1.0, which restores integratedTime verification against Fulcio certificate validity via PR #1185 and confirmed fix commits 4b7a49ebb1813f5b1ff113bcad63246358222d61 and b529335728fc5cfb574161b4b3c06859a8a2aa88. The vendor advisory is at https://github.com/sigstore/sigstore-java/security/advisories/GHSA-qqw8-7c2r-jxch. As an immediate compensating control for teams that cannot upgrade immediately, re-verify affected artifacts using an alternative current Sigstore client (e.g., cosign or sigstore-python), which do not carry this regression. Additionally, auditing Rekor transparency logs for signatures from potentially reused identities can surface unauthorized signing events. No configuration setting within sigstore-java 2.0.0 itself can disable or work around the missing check.