Fulcio allocates excessive memory during token parsing
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.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
github.com/sigstore/fulcioGo | < 1.8.3 | 1.8.3 |
Affected products
1Patches
1765a0e57608bMerge commit from fork (#2233)
1 file changed · +3 −3
pkg/identity/issuerpool.go+3 −3 modified@@ -41,11 +41,11 @@ func (p IssuerPool) Authenticate(ctx context.Context, token string, opts ...conf } func extractIssuerURL(token string) (string, error) { - parts := strings.Split(token, ".") - if len(parts) != 3 { - return "", fmt.Errorf("oidc: malformed jwt, expected 3 parts got %d", len(parts)) + if strings.Count(token, ".") != 2 { + return "", fmt.Errorf("oidc: malformed jwt, token must have 3 parts") } + parts := strings.SplitN(token, ".", 3) raw, err := base64.RawURLEncoding.DecodeString(parts[1]) if err != nil { return "", fmt.Errorf("oidc: malformed jwt payload: %w", err)
Vulnerability mechanics
Generated by null/stub on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.
References
4- github.com/advisories/GHSA-f83f-xpx7-ffpwghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2025-66506ghsaADVISORY
- github.com/sigstore/fulcio/commit/765a0e57608b9ef390e1eeeea8595b9054c63a5aghsax_refsource_MISCWEB
- github.com/sigstore/fulcio/security/advisories/GHSA-f83f-xpx7-ffpwghsax_refsource_CONFIRMWEB
News mentions
0No linked articles in our index yet.