Fulcio allocates excessive memory during token parsing

Function [identity.extractIssuerURL](https://github.com/sigstore/fulcio/blob/main/pkg/identity/issuerpool.go#L44-L45) currently splits (via a call to [strings.Split](https://pkg.go.dev/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. Relevant weakness: [CWE-405: Asymmetric Resource Consumption (Amplification)](https://cwe.mitre.org/data/definitions/405.html) Details See [identity.extractIssuerURL](https://github.com/sigstore/fulcio/blob/main/pkg/identity/issuerpool.go#L44-L45) Impact Excessive memory allocation

Source published

5 Dec 2025 18:18:26 UTC

Source modified

10 Sep 2026 03:50:58 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH