GHSA-f5mr-q85p-6hh6: github.com/sigstore/fulcio (CVE-2026-49478)

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

CVSS 8.7 HighEPSS 0.0028 · 20th percentile

Published by the GitHub Advisory Database at 30 Jun 2026, 18:38 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

Package	Ecosystem	Affected	Fixed in
github.com/sigstore/fulcio	Go	<1.8.6	1.8.6

Identifiers

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

Weakness (CWE)

CWE-918

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Fulcio, the Go package github.com/sigstore/fulcio, versions before 1.8.6 are vulnerable. Its OIDC discovery client followed cross-host redirects, which let a malicious or compromised issuer trigger blind server-side request forgery against internal systems, substitute attacker-controlled verification keys, and leak the in-cluster Kubernetes ServiceAccount token. Upgrade to version 1.8.6, which blocks cross-host redirects and restricts token use to the matching host; no other workaround is listed.

Written 1 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
8.7	High	3.1	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.0028, the 20th percentile, on 12 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 14:14 UTC First seen by agentprime
31 Oct 2026, 14:14 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.