CVE-2026-49478 Fulcio has OIDC Discovery Redirect Following Allows SSRF and JWKS Substitution for Meta-Issuer Paths, with Kubernetes Service-Account Token Leakage
A malicious OIDC issuer can trigger SSRF and leak Kubernetes ServiceAccount tokens by exploiting improper redirect handling in Fulcio.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-49478?
CVE-2026-49478 is a high-severity server-side request forgery vulnerability in sigstore fulcio, published on 13 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-918
Which versions are affected by CVE-2026-49478?
3 open source packages ship an affected version, including github.com/sigstore/fulcio.
| Package | Affected | Fixed in |
|---|---|---|
github.com/sigstore/fulcio Go | All versions | 1.8.6 |
github.com/sigstore/fulcio Go | All versions | 1.8.6 |
github.com/sigstore/fulcio Go | All versions | 1.8.6 |
How do I fix CVE-2026-49478?
Upgrade github.com/sigstore/fulcio to 1.8.6 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-49478 being exploited?
There is no known exploitation of CVE-2026-49478 in the wild and no public exploit code.
Sources
Also known as CLEANSTART-2026-IH01456, DEBIAN-CVE-2026-49478, GHSA-f5mr-q85p-6hh6, GO-2026-5853, MINI-28x7-4j7x-cppv, MINI-439j-4486-x5fp and 45 more.