Is CVE-2026-49478 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-49478 being exploited in the wild.

How severe is CVE-2026-49478?

High severity, with a CVSS score of 8.7, published 13 August 2026.

Which products and versions are affected?

github.com/sigstore/fulcio (Go) <= 1.8.5, SEMVER:introduced=0,fixed=1.8.6; Sigstore Fulcio <= 1.8.5.

Is there a fix for CVE-2026-49478?

Yes. github.com/sigstore/fulcio (Go): upgrade to 1.8.6 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-49478 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-49478?

Check whether you run github.com/sigstore/fulcio (Go) or Sigstore Fulcio at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-49478: Sigstore Fulcio SSRF and Token Leakage in OIDC Discovery

Q: Is there a fix for CVE-2026-49478?

Yes. github.com/sigstore/fulcio (Go): upgrade to 1.8.6 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

Q: How is CVE-2026-49478 attacked?

It is attacked over the network, in a software library.

Q: Am I affected by CVE-2026-49478?

Check whether you run github.com/sigstore/fulcio (Go) or Sigstore Fulcio at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-49478 · Severity: high · CVSS 8.7 · Published 2026-08-13

Sigstore Fulcio, a service used to issue certificates for secure software signing, contains vulnerabilities in how it handles identity provider connections. An attacker could trick the system into sending sensitive internal credentials to a malicious server or accept fraudulent security keys. This could allow an attacker to bypass security checks, forge digital signatures, or gain unauthorized access to internal Kubernetes environments.

Technologies: github.com/sigstore/fulcio (Go). Vendors: Go, Sigstore.

Quick answers

Is CVE-2026-49478 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-49478 being exploited in the wild.
How severe is CVE-2026-49478?: High severity, with a CVSS score of 8.7, published 13 August 2026.
Which products and versions are affected?: github.com/sigstore/fulcio (Go) <= 1.8.5, SEMVER:introduced=0,fixed=1.8.6; Sigstore Fulcio <= 1.8.5.
Is there a fix for CVE-2026-49478?: Yes. github.com/sigstore/fulcio (Go): upgrade to 1.8.6 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-49478 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-49478?: Check whether you run github.com/sigstore/fulcio (Go) or Sigstore Fulcio at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

github.com/sigstore/fulcio (Go): upgrade to 1.8.6 or later
```
go get github.com/sigstore/fulcio@v1.8.6
```

Technical details

Sigstore Fulcio's OIDC discovery client fails to validate cross-host redirects when fetching metadata from `/.well-known/openid-configuration`. This allows an attacker to perform blind SSRF or point the `jwks_uri` to a malicious host, leading to JWKS substitution and cache poisoning of verification keys. Additionally, Fulcio's transport layer globally attached Kubernetes ServiceAccount tokens to outbound requests, causing token leakage if an issuer redirected to a third-party domain or if a wildcard MetaIssuer matched an external endpoint. These issues are addressed in version 1.8.6 by blocking cross-host redirects and restricting token injection to exact host matches.

Affected products

Sigstore Fulcio <= 1.8.5

Identifiers

CVE-2026-49478
GHSA-f5mr-q85p-6hh6
GO-2026-5853

Timeline

2026-05-26: disclosed
2026-06-30: advisory: GitHub Advisory published

References

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