Signed payload type mutation via ASCII truncation
Published Jul 14, 2026 · Updated Jul 14, 2026
Improper signature verification in Sigstore sigstore-js before 3.2.1 allows attackers to alter a signed DSSE payload type. The @sigstore/core preAuthEncoding function encodes payloadType with Node.js ASCII semantics, truncating Unicode code points and producing identical signed bytes for distinct type strings. Exploitation requires control of a DSSE envelope after signing and submission to an affected verification workflow; the payload and signature remain unchanged while the asserted type changes.
Summary
What happened
Improper signature verification in Sigstore sigstore-js before 3.2.1 allows attackers to alter a signed DSSE payload type. The @sigstore/core preAuthEncoding function encodes payloadType with Node.js ASCII semantics, truncating Unicode code points and producing identical signed bytes for distinct type strings. Exploitation requires control of a DSSE envelope after signing and submission to an affected verification workflow; the payload and signature remain unchanged while the asserted type changes.
The record
- CVE
- CVE-2026-48758
- Published
- Jul 14, 2026
- Updated
- Jul 14, 2026
- Vendor
- Sigstore
- Product
- sigstore-js
- Classifications
- CWE-347, T1553
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Jul 14, 2026CVE publishedPublication date reported by the CVE source.
- Jul 14, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 3.2.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- DSSE payloadType mutation reproductionproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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