CVE-2026-58404CWE-918

Hugo security.http.urls deny rules bypassed by alternate IPv4 encodings

Medium · published July 6, 2026

CVSS v4.0
4.6
EPSS
0%
Percentile
29.5
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
4.6 · MEDIUM
Vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:N/SC:H/SI:N/SA:N
EPSS
0.00368 · 29.5th percentile
Weakness
CWE-918 · Server-Side Request Forgery (SSRF)
Published
2026-07-06T19:16Z
EPSS history
Timeline
  • 06 JUL 19:16Z
    Hugo security.http.urls deny rules bypassed by alternate IPv4 encodings
    cvelistv5