GHSA-jfc7-64v2-mr8c: @sigstore/core has DSSE payloadType type-binding failure
A vulnerability in the @sigstore/core package's preAuthEncoding function allows mutation of the DSSE payloadType after signing without invalidating the signature. This occurs because the function uses Node.js 'ascii' encoding, which truncates characters above U+00FF to their low byte, enabling Unicode characters to produce identical encoded bytes as ASCII characters. This breaks the DSSE type-binding guarantee. The issue affects versions prior to 3.2.1.
AI Analysis
Technical Summary
The preAuthEncoding function in @sigstore/core uses Node.js 'ascii' encoding to convert the Pre-Authentication Encoding (PAE) string to bytes. Since 'ascii' encoding is equivalent to 'latin1', characters above U+00FF are truncated to their low byte, allowing an attacker to substitute payloadType characters with Unicode variants that produce identical encoded bytes. This results in the payloadType being mutable after signing without signature invalidation, violating DSSE's type-binding guarantee. Additionally, the function uses JavaScript string length instead of UTF-8 byte length for payloadType length, contributing to the issue for non-ASCII types. This vulnerability is tracked as CVE-2026-48758 and affects @sigstore/core versions before 3.2.1.
Potential Impact
An attacker can alter the payloadType field after signing without causing signature verification to fail, breaking the intended type-binding security property of DSSE. This undermines the integrity guarantees of signed payloads, potentially allowing type confusion or misuse of signed data. The vulnerability does not affect confidentiality but impacts integrity and availability aspects as per CVSS vector. No known exploits are reported in the wild.
Mitigation Recommendations
A fix is available in @sigstore/core version 3.2.1 and later. Users should upgrade to version 3.2.1 or newer to resolve this issue. Until upgraded, be aware that signatures may not fully guarantee payloadType integrity due to this encoding flaw.
GHSA-jfc7-64v2-mr8c: @sigstore/core has DSSE payloadType type-binding failure
Description
A vulnerability in the @sigstore/core package's preAuthEncoding function allows mutation of the DSSE payloadType after signing without invalidating the signature. This occurs because the function uses Node.js 'ascii' encoding, which truncates characters above U+00FF to their low byte, enabling Unicode characters to produce identical encoded bytes as ASCII characters. This breaks the DSSE type-binding guarantee. The issue affects versions prior to 3.2.1.
CVSS v3.1
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The preAuthEncoding function in @sigstore/core uses Node.js 'ascii' encoding to convert the Pre-Authentication Encoding (PAE) string to bytes. Since 'ascii' encoding is equivalent to 'latin1', characters above U+00FF are truncated to their low byte, allowing an attacker to substitute payloadType characters with Unicode variants that produce identical encoded bytes. This results in the payloadType being mutable after signing without signature invalidation, violating DSSE's type-binding guarantee. Additionally, the function uses JavaScript string length instead of UTF-8 byte length for payloadType length, contributing to the issue for non-ASCII types. This vulnerability is tracked as CVE-2026-48758 and affects @sigstore/core versions before 3.2.1.
Potential Impact
An attacker can alter the payloadType field after signing without causing signature verification to fail, breaking the intended type-binding security property of DSSE. This undermines the integrity guarantees of signed payloads, potentially allowing type confusion or misuse of signed data. The vulnerability does not affect confidentiality but impacts integrity and availability aspects as per CVSS vector. No known exploits are reported in the wild.
Mitigation Recommendations
A fix is available in @sigstore/core version 3.2.1 and later. Users should upgrade to version 3.2.1 or newer to resolve this issue. Until upgraded, be aware that signatures may not fully guarantee payloadType integrity due to this encoding flaw.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-jfc7-64v2-mr8c
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-48758"]
- Ecosystems
- ["npm"]
- Database Specific Severity
- MODERATE
- Cvss Version
- 3.1
Threat ID: 6a3ef78d27e9c79719ff493d
Added to database: 06/26/2026, 22:05:01 UTC
Last enriched: 06/26/2026, 22:15:36 UTC
Last updated: 06/26/2026, 22:15:36 UTC
Views: 2
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