CVE-2026-49478
Received Received - Intake

Fulcio OIDC Redirect SSRF via ServiceAccount Token Exposure

Publication date: 2026-08-13

Last updated on: 2026-08-13

Assigner: GitHub, Inc.

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.

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Meta Information

Published
2026-08-13
Last Modified
2026-08-13
Generated
2026-08-13
AI Q&A
2026-08-13
EPSS Evaluated
N/A
NVD
CVE-2026-49478
EUVD
EUVD-2026-57859

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
sigstore fulcio to 1.8.6 (exc)
sigstore fulcio 1.8.6

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-918 The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.

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Executive Summary

Fulcio is a certificate authority for issuing code signing certificates using OpenID Connect (OIDC). Versions before 1.8.6 improperly handle cross-host redirects during OIDC discovery, allowing malicious issuers to perform blind SSRF attacks, substitute malicious JWKS keys, or leak Kubernetes ServiceAccount tokens to external hosts. Version 1.8.6 fixes this by blocking cross-host redirects and restricting token injection to exact host matches.

Detection Guidance

To detect this vulnerability, check if your Fulcio instance is running a version prior to 1.8.6. Use commands like 'fulcio version' or inspect deployment logs for version details. Monitor network traffic for unexpected cross-host redirects or unauthorized token exposure during OIDC discovery requests.

Impact Analysis

An attacker could exploit this to access internal systems via SSRF, replace verification keys to bypass signature validation, or steal Kubernetes ServiceAccount tokens. This could lead to unauthorized code signing, data breaches, or cluster compromise if tokens grant elevated access.

Compliance Impact

This vulnerability could lead to unauthorized data access or modification, violating GDPR's integrity and confidentiality requirements or HIPAA's safeguards for protected health information. Token leakage may also breach access control policies required by these regulations.

Mitigation Strategies

Upgrade Fulcio to version 1.8.6 or later immediately. This version blocks cross-host redirects and restricts token injection to exact host matches. No workarounds exist; upgrading is the only mitigation. Verify the upgrade by checking the version and testing OIDC discovery flows.

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