How severe is GHSA-59jp-pj84-45mr?

GHSA-59jp-pj84-45mr has a CVSS score of 5.8/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-59jp-pj84-45mr?

GHSA-59jp-pj84-45mr affects the following packages: github.com/sigstore/fulcio (Go). Ecosystems affected: Go.

How do I fix GHSA-59jp-pj84-45mr?

Update github.com/sigstore/fulcio to 1.8.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-59jp-pj84-45mr is resolved across your whole dependency graph.

How do I detect GHSA-59jp-pj84-45mr in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/sigstore/fulcio. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-59jp-pj84-45mr if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-59jp-pj84-45mr?

O3 pinpoints whether GHSA-59jp-pj84-45mr is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-59jp-pj84-45mr actively exploited in the wild?

No public exploit code has been indexed for GHSA-59jp-pj84-45mr yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-59jp-pj84-45mr?

GHSA-59jp-pj84-45mr has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 12th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-59jp-pj84-45mr?

GHSA-59jp-pj84-45mr is classified as Server-Side Request Forgery (SSRF) (CWE-918). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was GHSA-59jp-pj84-45mr published, and has it been updated?

GHSA-59jp-pj84-45mr was published on January 13, 2026 and was last updated on February 4, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

GHSA-59jp-pj84-45mr

MEDIUM

Fulcio is vulnerable to Server-Side Request Forgery (SSRF) via MetaIssuer Regex Bypass

Also known asCVE-2026-22772GO-2026-4311

Published

Jan 13, 2026

Updated

Feb 4, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk12th percentile+0.21%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

1 pkg affected

🐹github.com/sigstore/fulcio

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

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)

func metaRegex(issuer string) (*regexp.Regexp, error) {
    quoted := regexp.QuoteMeta(issuer)
    replaced := strings.ReplaceAll(quoted, regexp.QuoteMeta("*"), "[-_a-zA-Z0-9]+")
    return regexp.Compile(replaced)  // Missing ^ and $ anchors
}

The Bug

The regex has no ^ (start) or $ (end) anchors. Go's regexp.MatchString() does substring matching, so:

Pattern:  https://oidc.eks.*.amazonaws.com/id/*
Regex:    https://oidc\.eks\.[-_a-zA-Z0-9]+\.amazonaws\.com/id/[-_a-zA-Z0-9]+

Input:    https://attacker.com/x/https://oidc.eks.foo.amazonaws.com/id/bar
Result:   MATCHES (substring found)

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

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/sigstore/fulcio`	all versions	1.8.5

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/sigstore/fulcio. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/sigstore/fulcio to 1.8.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-59jp-pj84-45mr is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-59jp-pj84-45mr is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-59jp-pj84-45mr. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

# 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](https://portswigger.net/web-security/ssrf/blind). ## Impact - SSRF to cloud metadata (169.254.169.254) - S

O3 Security · Impact-Aware SCA

Is GHSA-59jp-pj84-45mr in your dependencies?

O3 detects GHSA-59jp-pj84-45mr across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works

GHSA-59jp-pj84-45mr

EPSS Exploitation Probability

Blast Radius

Description

Security Disclosure: SSRF via MetaIssuer Regex Bypass

Summary

Impact

Patches

Workarounds

Affected Code

The Bug

Exploit

Affected Packages

Detection & mitigation playbook

Detect

Fix

Workarounds

How O3 protects you

Frequently Asked Questions

Is GHSA-59jp-pj84-45mr in your dependencies?