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.
Published: 2025-12-04
Score: 7.5 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-f83f-xpx7-ffpw Fulcio allocates excessive memory during token parsing
History

Tue, 10 Mar 2026 19:45:00 +0000

Type Values Removed Values Added
First Time appeared Linuxfoundation
Linuxfoundation fulcio
CPEs cpe:2.3:a:linuxfoundation:fulcio:*:*:*:*:*:*:*:*
Vendors & Products Linuxfoundation
Linuxfoundation fulcio

Thu, 11 Dec 2025 12:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

 threat_severity

Important

Fri, 05 Dec 2025 16:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Fri, 05 Dec 2025 11:00:00 +0000

Type Values Removed Values Added
First Time appeared Sigstore
Sigstore fulcio
Vendors & Products Sigstore
Sigstore fulcio

Thu, 04 Dec 2025 22:15:00 +0000

Type Values Removed Values Added
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.
Title Fulcio allocates excessive memory during token parsing
Weaknesses CWE-405
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Subscriptions

Linuxfoundation Fulcio
Sigstore Fulcio
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2025-12-05T15:32:25.591Z

Reserved: 2025-12-03T15:12:22.978Z

Link: CVE-2025-66506

cve-icon Vulnrichment

Updated: 2025-12-05T15:32:21.138Z

cve-icon NVD

Status : Analyzed

Published: 2025-12-04T22:15:49.503

Modified: 2026-03-10T19:30:53.470

Link: CVE-2025-66506

cve-icon Redhat

Severity : Important

Publid Date: 2025-12-04T22:04:41Z

Links: CVE-2025-66506 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2025-12-05T10:52:21Z

Weaknesses