Vulnerabilities in pkg:npm/@sigstore/core

PACKAGE
Advisory Identifier: GHSA-jfc7-64v2-mr8c
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Advisory Summary

CVE-2026-48758 is a MODERATE (CVSS 5.4) @sigstore/core has dsse payloadtype type-binding vulnerability (CWE-347: Improper Verification of Cryptographic Signature) affecting @sigstore/core libraries in the npm ecosystem. The issue involves @sigstore/core has dsse payloadtype type-binding failure. Remediation is available by upgrading affected packages to version 3.2.1.

1 Known Advisory Record(s)
Package Vulnerability Intelligence

pkg:npm/@sigstore/core

1 Known Advisory Record(s)

Vulnerability advisories affecting package pkg:npm/@sigstore/core. Select an advisory below to view technical details or fixes.

Advisory ID CVE / NVD Severity Summary
GHSA-jfc7-64v2-mr8c CVE-2026-48758 MODERATE @sigstore/core has DSSE payloadType type-binding failure

CVE-2026-48758 at a Glance

CVE Identifier CVE-2026-48758
GHSA Identifier GHSA-jfc7-64v2-mr8c
Severity MODERATE
CVSS v3.1 Base Score 5.4
CWE Classification CWE-347: Improper Verification of Cryptographic Signature
Affected Product @sigstore/core
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.4

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2026-48758

To remediate this vulnerability, upgrade all affected @sigstore/core dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

@sigstore/core fixed: 3.2.1 
npm install @sigstore/core@3.2.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls @sigstore/core

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-48758, inspect your project dependencies using npm:

npm ls @sigstore/core

Analyze the terminal output to locate any version of @sigstore/core in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.2.1), your application is affected.

Note: The npm ls @sigstore/core command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-347: Improper Verification of Cryptographic Signature, where the product does not verify, or incorrectly verifies, the cryptographic signature for data. In @sigstore/core, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact The `preAuthEncoding` function in `@sigstore/core` uses Node.js `'ascii'` encoding when converting the PAE (Pre-Authentication Encoding) string to bytes. This allows `payloadType` to be mutated after signing without invalidating the signature, breaking the type-binding guarantee that DSSE is designed to provide. In `packages/core/src/dsse.ts`, the PAE function builds a string containing `payloadType` and then encodes it with `Buffer.from(prefix, 'ascii')`. In Node.js, `'ascii'` encoding for string-to-Buffer is equivalent to `'latin1'`, which **truncates characters above U+00FF to their low byte**. This means for any ASCII character, there exist Unicode characters (at U+01xx, U+02xx, etc.) that produce the identical encoded byte: | Original | Codepoint | Mutant | Codepoint | Encoded byte | |----------|-----------|--------|-----------|--------------| | `t` | U+0074 | `Ŵ` | U+0174 | `0x74` | | `e` | U+0065 | `ť` | U+0165 | `0x65` | An attacker can substitute every character in `payloadType` with a Unicode variant whose low byte matches, producing **identical PAE bytes** and a passing signature verification. Additionally, `payloadType.length` returns the JavaScript string length (UTF-16 code units) rather than the UTF-8 byte length required by the DSSE spec, though this is only a contributing factor for non-ASCII types. #### Reproduction ```javascript const { preAuthEncoding } = require('@sigstore/core/dist/dsse.js'); const payload = Buffer.from('hello world'); const original = preAuthEncoding('text/plain', payload); // U+01xx chars whose low bytes match the original ASCII chars const mutant = preAuthEncoding('\u0174\u0165\u0178\u0174/\u0170\u016c\u0161\u0169\u016e', payload); console.log('PAE bytes equal:', original.equals(mutant)); // true — should be false ```

CVE-2026-48758 Affected @sigstore/core Versions

1 component(s)
Fixed Versions:
3.2.1
Product / Package Ecosystem Affected Versions Fixed Version
@sigstore/core
npm/@sigstore/core
npm
< 3.2.1
3.2.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/sigstore/sigstore-js/security/advisories/GHSA-jfc7-64v2-mr8c
@sigstore/core Source Repository REPOSITORY
https://github.com/sigstore/sigstore-js

Frequently Asked Questions

What is CVE-2026-48758?
CVE-2026-48758 is a security vulnerability in @sigstore/core involving @sigstore/core has DSSE payloadType type-binding failure under CWE-347: Improper Verification of Cryptographic Signature.
Which @sigstore/core versions are affected?
Affected versions include releases prior to 3.2.1 across affected packages: @sigstore/core.
What version fixes CVE-2026-48758?
Upgrading to 3.2.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is @sigstore/core affected?
Yes, @sigstore/core is affected in releases prior to 3.2.1. Upgrade your dependency to 3.2.1 or later.
What is the CVSS score of CVE-2026-48758?
CVE-2026-48758 has a CVSS v3.1 base score of 5.4 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L.
What CWE is associated with CVE-2026-48758?
CVE-2026-48758 is classified under CWE-347: Improper Verification of Cryptographic Signature (The product does not verify, or incorrectly verifies, the cryptographic signature for data.).
How can I check npm dependencies for CVE-2026-48758?
Run the dependency tree command: 'npm ls @sigstore/core'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-jfc7-64v2-mr8c",
  "modified" : "2026-06-26T19:11:20Z",
  "published" : "2026-06-26T19:11:19Z",
  "aliases" : [ "CVE-2026-48758" ],
  "summary" : "@sigstore/core has DSSE payloadType type-binding failure",
  "details" : "### Impact\nThe `preAuthEncoding` function in `@sigstore/core` uses Node.js `'ascii'` encoding when converting the PAE (Pre-Authentication Encoding) string to bytes. This allows `payloadType` to be mutated after signing without invalidating the signature, breaking the type-binding guarantee that DSSE is designed to provide.\n\nIn `packages/core/src/dsse.ts`, the PAE function builds a string containing `payloadType` and then encodes it with `Buffer.from(prefix, 'ascii')`.\n\nIn Node.js, `'ascii'` encoding for string-to-Buffer is equivalent to `'latin1'`, which **truncates characters above U+00FF to their low byte**. This means for any ASCII character, there exist Unicode characters (at U+01xx, U+02xx, etc.) that produce the identical encoded byte:\n\n| Original | Codepoint | Mutant | Codepoint | Encoded byte |\n|----------|-----------|--------|-----------|--------------|\n| `t`      | U+0074    | `Ŵ`    | U+0174    | `0x74`       |\n| `e`      | U+0065    | `ť`    | U+0165    | `0x65`       |\n\nAn attacker can substitute every character in `payloadType` with a Unicode variant whose low byte matches, producing **identical PAE bytes** and a passing signature verification.\n\nAdditionally, `payloadType.length` returns the JavaScript string length (UTF-16 code units) rather than the UTF-8 byte length required by the DSSE spec, though this is only a contributing factor for non-ASCII types.\n\n#### Reproduction\n\n```javascript\nconst { preAuthEncoding } = require('@sigstore/core/dist/dsse.js');\nconst payload = Buffer.from('hello world');\n\nconst original = preAuthEncoding('text/plain', payload);\n// U+01xx chars whose low bytes match the original ASCII chars\nconst mutant = preAuthEncoding('\\u0174\\u0165\\u0178\\u0174/\\u0170\\u016c\\u0161\\u0169\\u016e', payload);\n\nconsole.log('PAE bytes equal:', original.equals(mutant)); // true — should be false\n```",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@sigstore/core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.2.1"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 3.2.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/sigstore/sigstore-js/security/advisories/GHSA-jfc7-64v2-mr8c"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/sigstore/sigstore-js"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-347" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-26T19:11:19Z",
    "nvd_published_at" : null
  }
}