CVE-2026-48791 is a low-severity (CVSS 2) CWE-347 vulnerability in dev.sigstore:sigstore-java. A fix is available for dev.sigstore:sigstore-java — see the affected versions and patch details below.
Sigstore Java has a vulnerability with bundle verification of integratedTime
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-48791.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-48791 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 395,249 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
dev.sigstore:sigstore-javaReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
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 [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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | dev.sigstore:sigstore-java | ≥ 2.0.0&&< 2.1.0 | 2.1.0dev.sigstore:sigstore-java:2.1.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for dev.sigstore:sigstore-java, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update dev.sigstore:sigstore-java to 2.1.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-48791 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2026-48791 in your dependencies?
Find it across Maven, including transitive dependencies.