CVE-2026-49478

Fulcio has OIDC Discovery Redirect Following Allows SSRF and JWKS Substitution for Meta-Issuer Paths, with Kubernetes Service-Account Token Leakage

Published Aug 13, 2026 CVSS 3.1 · 8.7 High EPSS < 1% KEV · Not listed
Description
Fulcio is a certificate authority for issuing code signing certificates for an OpenID Connect (OIDC) identity. Versions through 1.8.5 improperly follow cross-host redirects and attach Kubernetes ServiceAccount tokens during OIDC discovery, allowing a malicious or compromised issuer to perform blind SSRF, substitute and cache malicious JWKS keys, or disclose ServiceAccount tokens to external hosts. Version 1.8.6 blocks cross-host redirects, restricts token injection, and restricts local token loading. No known workarounds are available.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-f5mr-q85p-6hh6 Fulcio has OIDC Discovery Redirect Following Allows SSRF and JWKS Substitution for Meta-Issuer Paths, with Kubernetes Service-Account Token Leakage
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description A flaw was found in Fulcio's OpenID Connect (OIDC) Discovery client. This vulnerability allows a remote attacker to perform Server-Side Request Forgery (SSRF) by redirecting discovery requests to internal systems. Additionally, an attacker can manipulate the JSON Web Key Set (JWKS) Uniform Resource Identifier (URI) to poison the verifier cache with malicious keys, enabling the validation of attacker-controlled signatures. Furthermore, the flaw can lead to the leakage of Kubernetes ServiceAccount tokens to third-party hosts through cross-host redirects or misconfigured MetaIssuers, potentially exposing sensitive cluster credentials. Fulcio is a certificate authority for issuing code signing certificates for an OpenID Connect (OIDC) identity. Versions through 1.8.5 improperly follow cross-host redirects and attach Kubernetes ServiceAccount tokens during OIDC discovery, allowing a malicious or compromised issuer to perform blind SSRF, substitute and cache malicious JWKS keys, or disclose ServiceAccount tokens to external hosts. Version 1.8.6 blocks cross-host redirects, restricts token injection, and restricts local token loading. No known workarounds are available.
Title github.com/sigstore/fulcio: Fulcio: Server-Side Request Forgery and Kubernetes ServiceAccount token leakage Fulcio has OIDC Discovery Redirect Following Allows SSRF and JWKS Substitution for Meta-Issuer Paths, with Kubernetes Service-Account Token Leakage
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N'}

cvssV3_1

{'score': 8.7, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N'}

Type Values Removed Values Added
Description A flaw was found in Fulcio's OpenID Connect (OIDC) Discovery client. This vulnerability allows a remote attacker to perform Server-Side Request Forgery (SSRF) by redirecting discovery requests to internal systems. Additionally, an attacker can manipulate the JSON Web Key Set (JWKS) Uniform Resource Identifier (URI) to poison the verifier cache with malicious keys, enabling the validation of attacker-controlled signatures. Furthermore, the flaw can lead to the leakage of Kubernetes ServiceAccount tokens to third-party hosts through cross-host redirects or misconfigured MetaIssuers, potentially exposing sensitive cluster credentials.
Title github.com/sigstore/fulcio: Fulcio: Server-Side Request Forgery and Kubernetes ServiceAccount token leakage
Weaknesses CWE-918
References
Metrics threat_severity

None

cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N'}

threat_severity

Moderate

Subscriptions

No data.

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Aug 15, 2026, 3:14 AM
Reserved
May 30, 2026, 4:17 AM
Status
Deferred
Published
Aug 13, 2026, 1:19 PM
Modified
Oct 24, 2026, 4:10 PM
Severity
Moderate
Public date
Jun 30, 2026, 6:40 PM