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.

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.

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 Jwt Attack Java

2.0

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory 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 GitHub Advisory.

CVSS VectorGitHub Advisory

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

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.

DescriptionGitHub Advisory

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. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access

Compromise target developer workstation locally

Delivery

Exfiltrate ephemeral Sigstore private key from signing session

Exploit

Construct forged bundle using expired Fulcio certificate

Execution

Present forged bundle to sigstore-java 2.0.0 verifier

Persist

Bypass integratedTime validity check

Impact

Artifact accepted as legitimately signed

Access

Compromise target developer workstation locally

Delivery

Exfiltrate ephemeral Sigstore private key from signing session

Exploit

Construct forged bundle using expired Fulcio certificate

Execution

Present forged bundle to sigstore-java 2.0.0 verifier

Persist

Bypass integratedTime validity check

Impact

Artifact accepted as legitimately signed

Vulnerability AssessmentAI

Exploitation	Exploitation requires the attacker to have already obtained local system access AND to have successfully exfiltrated the ephemeral private key used during a prior Sigstore signing operation - the vendor description explicitly names this as the required precondition. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment	The CVSS 3.1 vector (AV:L/AC:L/PR:H/UI:R/S:U/C:N/I:L/A:N) yielding a score of 2.0 accurately reflects a very constrained attack surface: local-only access, high privilege (sufficient to exfiltrate a temporary signing key from a user's session), and required victim interaction (triggering bundle verification). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario	An attacker who has already compromised a developer workstation and exfiltrated the ephemeral private key generated during a prior Sigstore signing session crafts a forged bundle pairing that key with the original, now-expired Fulcio certificate. When a pipeline or developer invokes `sigstore-cli verify` (or the sigstore-java library directly) on the forged bundle using version 2.0.0, the missing `integratedTime` check causes verification to succeed silently - a result the vendor-provided PoC bundle demonstrates explicitly against the CLI tool.
Remediation	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. … Detailed patch versions, workarounds, and compensating controls in full report.