CVE-2026-58404
CVE-2026-58404 is a Server-Side Request Forgery (SSRF) vulnerability in github.com/gohugoio/hugo. O3 Security confirms whether CVE-2026-58404 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Hugo security.http.urls deny rules bypassed by alternate IPv4 encodings
Blast Radius
github.com/gohugoio/hugoReal-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
Hugo is a static site generator. From v0.162.0 through v0.163.0, the default security.http.urls policy denies requests to loopback, internal, and cloud-metadata IPv4 literals, but the deny rule only matched dotted-decimal notation, so alternate IPv4 encodings of the same addresses, including integer, hex, or octal, passed the policy. When a template passes an untrusted or data-derived URL to resources.GetRemote and the host platform uses the cgo system resolver, these encodings resolve to the blocked address, allowing build-time server-side requests to loopback and internal services, including the cloud-metadata endpoint in hosted or CI builds; the same check is reused on redirects, so the gap also applies to each redirect hop. This issue is fixed in v0.163.1.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/gohugoio/hugo | ≥ 0.162.0&&< 0.163.1 | 0.163.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/gohugoio/hugo. 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/gohugoio/hugo to 0.163.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-58404 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 CVE-2026-58404 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 CVE-2026-58404. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-58404 in your dependencies?
O3 detects CVE-2026-58404 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.