CVE-2025-66506

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.

CVSS v3.1 Score

7.5

HIGH

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

Weakness Type (CWE)

CWE-405 CWE-405

Affected Products

Vendor	Product	Versions
linuxfoundation	fulcio	< 1.8.3

References

Advisories & Patches

https://github.com/sigstore/fulcio/commit/765a0e57608b9ef390e1eeeea8595b9054c63a5a https://github.com/sigstore/fulcio/security/advisories/GHSA-f83f-xpx7-ffpw

Frequently Asked Questions

What is CVE-2025-66506? +

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. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2025-66506? +

CVE-2025-66506 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-66506? +

CVE-2025-66506 affects products from linuxfoundation, specifically: fulcio. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-66506? +

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.

Related Vulnerabilities

CVE-2025-53633 9.8

Chall-Manager is a platform-agnostic system able to start Challenges on Demand of a player. When decoding a scenario (i.e. a …

CVE-2024-56200 8.6

Altair is a fork of Misskey v12. Affected versions lack of request validation and lack of authentication in the image …

CVE-2025-42874 7.9

SAP NetWeaver remote service for Xcelsius allows an attacker with network access and high privileges to execute arbitrary code on …

CVE-2025-8677 7.5

Querying for records within a specially crafted zone containing certain malformed DNSKEY records can lead to CPU exhaustion. This issue …

CVE-2024-34703 7.5

Botan is a C++ cryptography library. X.509 certificates can identify elliptic curves using either an object identifier or using explicit …

CVE-2025-30204 7.5

golang-jwt is a Go implementation of JSON Web Tokens. Starting in version 3.2.0 and prior to versions 5.2.2 and 4.5.2, …