CVE-2026-22772 is a medium-severity server-side request forgery (SSRF) vulnerability in github.com/sigstore/fulcio (go), affecting versions <= 1.8.4. It is fixed in 1.8.5.
Security Disclosure: SSRF via MetaIssuer Regex Bypass Summary Fulcio's metaRegex() function uses unanchored regex, allowing attackers to bypass MetaIssuer URL validation and trigger SSRF to arbitrary internal services. Since the SSRF only can trigger GET requests, the request cannot mutate state. The response from the GET request is not returned to the caller so data exfiltration is not possible. A malicious actor could attempt to probe an internal network through Blind SSRF. Impact SSRF to cloud metadata (169.254.169.254) SSRF to internal Kubernetes APIs SSRF to any service accessible from Fulcio's network Affects ALL deployments using MetaIssuers Patches Upgrade to v1.8.5. Workarounds None. If anchors are included in the meta issuer configuration URL, they will be escaped before the regular expression is compiled, not making this a sufficient mitigation. Deployments must upgrade to the latest Fulcio release v1.8.5. Affected Code File: pkg/config/config.go Function: metaRegex() (lines 143-156) The Bug The regex has no ^ (start) or $ (end) anchors. Go's regexp.MatchString() does substring matching, so: Exploit Attacker sends JWT with iss claim: https://attacker.com/path/https://oidc.eks.x.amazonaws.com/id/y Fulcio's GetIssuer() matches this against MetaIssuer patterns Unanchored regex matches the embedded pattern as substring Fulcio calls oidc.NewProvider() with attacker's URL HTTP request goes to attacker.com, not amazonaws.com Attacker returns OIDC discovery with jwks_uri pointing to internal service Fulcio fetches from internal service → SSRF
Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.
CVE-2026-22772 has a CVSS score of 5.8 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (1.8.5). Upgrading removes the vulnerable code path.
go
github.com/sigstore/fulcio (<= 1.8.4)github.com/sigstore/fulcio → 1.8.5 (go)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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Already deployed Kodem? See CVE-2026-22772 in your environment →Upgrade github.com/sigstore/fulcio to 1.8.5 or later to resolve this vulnerability.
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CVE-2026-22772 is a medium-severity server-side request forgery (SSRF) vulnerability in github.com/sigstore/fulcio (go), affecting versions <= 1.8.4. It is fixed in 1.8.5. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
CVE-2026-22772 has a CVSS score of 5.8 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
github.com/sigstore/fulcio (go) versions <= 1.8.4 is affected.
Yes. CVE-2026-22772 is fixed in 1.8.5. Upgrade to this version or later.
Whether CVE-2026-22772 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade github.com/sigstore/fulcio to 1.8.5 or later.