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High severityNVD Advisory· Published Dec 4, 2025· Updated Dec 5, 2025

Fulcio allocates excessive memory during token parsing

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.

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Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
github.com/sigstore/fulcioGo
< 1.8.31.8.3

Affected products

182

Patches

Vulnerability mechanics

References

4

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