SSRF (Server-Side Request Forgery) in github.com/sigstore/fulcio (CVE-2026-49478)
Summary
SSRF in github.com/sigstore/fulcio (CVE-2026-49478). Confidential information can be exposed externally. Exploitable via jwks_uri. Mitigation: upgrade to 1.8.6 or later.
Original description
The description as published by the source.
Impact
Three security vulnerabilities were identified in the OIDC Discovery client:
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Blind Server-Side Request Forgery (SSRF) via Cross-Host Redirects:
Fulcio uses an HTTP client to fetch OIDC discovery metadata (/.well-known/openid-configuration). Prior to this fix, if a configured issuer returned an HTTP redirect to a different host, the client followed it by default. This allowed a compromised or malicious issuer to redirect Fulcio's discovery requests to internal-only systems, resulting in blind SSRF. -
JWKS Substitution and Cache Poisoning:
Because cross-host redirects were permitted during OIDC discovery, an attacker could manipulate the discovery flow to return a maliciousjwks_uripointing to an attacker-controlled host. When Fulcio successfully initialized the provider and cached the resulting verifier in the verifier cache, it poisoned the cache with the attacker's verification keys. The attacker could then present signatures validated against the poisoned keys. -
Kubernetes ServiceAccount Token Leakage:
Fulcio mounts an in-cluster Kubernetes ServiceAccount token to authenticate OIDC discovery requests sent to the local control plane API server (https://kubernetes.default.svc).- Cross-Host Redirects & JWKS: The token was previously attached globally by the transport, leaking it to third-party hosts if the issuer performed a redirect or if the
jwks_uripointed to a different domain. - Wildcard MetaIssuers: If a w…
- Cross-Host Redirects & JWKS: The token was previously attached globally by the transport, leaking it to third-party hosts if the issuer performed a redirect or if the
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-49478 has been found in github.com/sigstore/fulcio.
Attackers can target a specific entry point like jwks_uri over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 8.7/10.
What to do: upgrade github.com/sigstore/fulcio to 1.8.6 or later.
If unsure, ask your IT team or search "github.com/sigstore/fulcio CVE-2026-49478" on the vendor's site.
CVE-2026-49478 (github.com/sigstore/fulcio) — CWE-918 / CVSS v3 8.7
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: jwks_uri / MetaIssuer / kubernetes
Patched: 1.8.6 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
SSRF (CWE-918) exists in github.com/sigstore/fulcio. Attackers reach the vulnerable code path via jwks_uri without authentication.
Check the vendor advisory for the affected versions of github.com/sigstore/fulcio. Attack surface: jwks_uri / MetaIssuer / kubernetes.
Severity: High (CVSS 8.7/10). Confidential information can be exposed externally.
Update to 1.8.6.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'github.com/sigstore/fulcio' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'github.com/sigstore/fulcio' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
github.com/sigstore/fulcioを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade github.com/sigstore/fulcio to 1.8.6ステージング環境で 1.8.6 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
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3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-49478 golang-github-sigstore-fulcio
- Ubuntu UBUNTU-CVE-2026-49478 golang-github-sigstore-fulcio