CVE-2026-48758 sigstore CVE debrief

Who should care

Defenders responsible for maintaining and securing software supply chains using Sigstore services should assess exposure and verify their usage of the affected @sigstore/core library.

Why it matters

CVE-2026-48758 allows signature bypass in sigstore-js, impacting the security and integrity of software supply chains using Sigstore services. Defenders should prioritize verification and updates to maintain the type-binding guarantee.

• Signature bypass may allow for unauthorized modifications to software artifacts
• Type-binding guarantee of DSSE may be compromised, potentially leading to security risks

Technical summary

The preAuthEncoding function in @sigstore/core uses Node.js ascii encoding when converting the PAE string to bytes, allowing payloadType to be mutated after signing without invalidating the signature and breaking the type-binding guarantee that DSSE is designed to provide. This issue is fixed in version 3.2.1. The vulnerability impacts the security of software supply chains that rely on Sigstore services for ensuring the integrity and authenticity of software artifacts. The improper encoding allows for a potential attacker to modify the payload type after it has been signed, which could lead to unauthorized modifications of software artifacts. This undermines the trust and security provided by the DSSE (Digital

Defensive priority

Defenders should prioritize verifying and updating @sigstore/core to version 3.2.1 or later, and review their usage of Sigstore services to ensure the type-binding guarantee is maintained.

Recommended defensive actions

• Verify and update @sigstore/core to version 3.2.1 or later
• Review usage of Sigstore services to ensure type-binding guarantee is maintained
• Monitor for potential signature bypass attempts
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The CVE record and NVD entry provide details on the vulnerability in sigstore-js, specifically in the @sigstore/core library. The issue allows payloadType to be mutated after signing without invalidating the signature, breaking the type-binding guarantee of DSSE.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.