CVE-2026-48758 in sigstore-js
Summary
by MITRE • 07/15/2026
sigstore-js provides JavaScript libraries for interacting with Sigstore services. Prior to 3.2.1, 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.
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Analysis
by VulDB Data Team • 07/15/2026
The sigstore-js library represents a critical security vulnerability in the cryptographic signature verification process that undermines fundamental security assurances provided by the DSSE (Developer Scripted Software Signing) specification. This flaw affects versions prior to 3.2.1 of the @sigstore/core package where the preAuthEncoding function employs Node.js ascii encoding during PAE (Pre-Auth Encoding) string conversion to bytes. The vulnerability stems from an improper handling of payload type information within the signing process, creating a scenario where malicious actors can modify the payloadType field after signature generation without detection.
The technical implementation flaw resides in the encoding mechanism used for converting the PAE string to bytes, which fails to maintain strict type binding between the payload content and its associated metadata. When Node.js ascii encoding is utilized instead of a more rigorous byte-level conversion, it creates ambiguity in how the payloadType parameter is processed during signature validation. This design weakness directly violates the core principle of DSSE that establishes strong type binding between the signed content and its metadata, ensuring that signatures cannot be transferred between different payload types without detection.
The operational impact of this vulnerability extends beyond simple signature validation failures to compromise the entire trust model of software supply chain security systems. Attackers can exploit this weakness by generating a valid signature for one payload type and then modifying the payloadType field in subsequent operations, effectively bypassing the type-binding mechanism that DSSE was specifically designed to prevent. This creates a dangerous scenario where unsigned or malicious content could be accepted as legitimate due to the compromised signature validation process, undermining the integrity guarantees that organizations rely upon for secure software distribution.
Security practitioners should recognize this vulnerability as aligning with CWE-295 which addresses improper certificate validation and CWE-347 which covers improper validation of cryptographic signatures. The flaw also maps to ATT&CK technique T1553.006 related to credential access through signature validation bypasses, potentially enabling attackers to manipulate software supply chain components. Organizations using sigstore-js versions prior to 3.2.1 must urgently implement mitigation strategies including immediate version upgrades, comprehensive security code reviews, and enhanced monitoring of signature validation processes. The fix in version 3.2.1 addresses the core encoding issue by implementing proper byte-level conversion that maintains strict type binding throughout the signing and verification lifecycle, restoring the intended security guarantees of the DSSE specification.
This vulnerability demonstrates the critical importance of maintaining strict adherence to cryptographic protocol specifications in software supply chain security tools. The failure to properly handle payload type information during signature generation creates a fundamental weakness that can be exploited across multiple attack vectors, potentially compromising entire software distribution pipelines and undermining trust in digital signatures used for code authentication and integrity verification.