CVE-2025-66506Fulcio is a free-to-use certificate authority for issuing code signing certificates for an OpenID Connect (OIDC) identity.
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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.
- CVSS
- 7.5 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-405
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Analyzed
- Record last updated
- Oct 18, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
linuxfoundation fulcio linuxfoundation:fulcio | before 1.8.3 | NVD |
References
- https://github.com/sigstore/fulcio/commit/765a0e57608b9ef390e1eeeea8595b9054c63a5apatch
- https://github.com/sigstore/fulcio/security/advisories/GHSA-f83f-xpx7-ffpwvendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.