Summary
Sigstore Java has a vulnerability with bundle verification of integratedTime
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 [email protected]: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.
CVE-2026-48791 has a CVSS score of 2.0 (Low). The vector is requires local access, high privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.1.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-48791? CVE-2026-48791 is a low-severity security vulnerability in dev.sigstore:sigstore-java (maven), affecting versions = 2.0.0. It is fixed in 2.1.0.
- How severe is CVE-2026-48791? CVE-2026-48791 has a CVSS score of 2.0 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of dev.sigstore:sigstore-java are affected by CVE-2026-48791? dev.sigstore:sigstore-java (maven) versions = 2.0.0 is affected.
- Is there a fix for CVE-2026-48791? Yes. CVE-2026-48791 is fixed in 2.1.0. Upgrade to this version or later.
- Is CVE-2026-48791 exploitable, and should I be worried? Whether CVE-2026-48791 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-48791 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-48791? Upgrade
dev.sigstore:sigstore-javato 2.1.0 or later.