CVE-2026-48758: Signature Bypass (CVSS 5.4)

Description

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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CVSS v3.1 Score

5.4

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L

EPSS — Exploit Prediction

0.0026

Probability of exploitation

0.18%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-347 CWE-347

References

Other References

https://github.com/sigstore/sigstore-js/commit/b5aa4f1f8d2db0a9dfa6430fb114d9c2f1c304f7 https://github.com/sigstore/sigstore-js/pull/1657 https://github.com/sigstore/sigstore-js/releases/tag/%40sigstore%2Fcore%403.2.1 https://github.com/sigstore/sigstore-js/security/advisories/GHSA-jfc7-64v2-mr8c https://github.com/sigstore/sigstore-js/security/advisories/GHSA-jfc7-64v2-mr8c

Frequently Asked Questions

What is CVE-2026-48758? +

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. It has a CVSS v3.1 base score of 5.4 (MEDIUM).

How severe is CVE-2026-48758? +

CVE-2026-48758 has a CVSS v3.1 score of 5.4 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0026, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-48758? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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