🛡️ CVE-2025-66506

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-405 NVD
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Fulcio is a free-to-use certificate authority for issuing code signing certificates for an OpenID Connect (OIDC) identity. Prior to 1.8.3, function identity.extractIssuerURL splits (via a call to strings.Split) its argument (which is untrusted data) on periods. As a result, in the face of a malicious request with an (invalid) OIDC identity token in the payload containing many period characters, a call to extractIssuerURL incurs allocations to the tune of O(n) bytes (where n stands for the length of the function's argument), with a constant factor of about 16. This vulnerability is fixed in 1.8.3.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

Affected software and timeline

Affected software: fulcio (fixed in 1.8.3) and github.com/sigstore/fulcio. Published on 4 December 2025 and last revised on 10 March 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE CWE-405
Public Exploit ✅ No
Source NVD
Published 2025-12-04
Updated 2026-06-15
Modified 2026-03-10

Affected Packages

Software From version Fixed in
fulcio — 1.8.3
github.com/sigstore/fulcio — —

Similar Threats

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