GHSA-FW87-FV5R-9FPW

Vulnerability from github – Published: 2026-06-16 20:12 – Updated: 2026-06-16 20:12
VLAI
Summary
Hugo: Symlink confinement bypass in resources.Get
Details

Commit: f8b5fa09a6 — Fix prevention of direct symlink reads in resources.Get Affected versions: v0.123.0 through v0.161.1. Earlier versions are not affected. Fixed in: v0.162.0. Severity: Medium. Requires the attacker to be able to place (or convince a site author to place) a symlink inside a mounted directory — for example, inside a locally-vendored theme under themes/. Themes mounted as Go modules from GitHub have symlinks stripped on download and are not affected. Multi-directory walks (e.g. content/asset walking) were not affected either; only direct lookups via resources.Get followed symlinks.

Description. Hugo's virtual filesystem is designed so that files under a mount cannot reach outside the mount tree. A regression introduced in v0.123.0 caused RootMappingFs.statRoot to call Stat (which follows symlinks) instead of Lstat, so a direct resources.Get "somefile" where somefile was a symlink pointing outside the mount would return the target's contents. This effectively let a symlink planted inside a theme or local mount read arbitrary files reachable to the user running hugo.

Mitigation. v0.162.0 calls LstatIfPossible and rejects symlinked entries with os.ErrNotExist, matching the behaviour of pre-v0.123.0 releases and of the directory-walking code paths.

Severity
6.9 (Medium)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/gohugoio/hugo"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.123.0"
            },
            {
              "fixed": "0.162.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-50135"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-59"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-16T20:12:34Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "**Commit:** [f8b5fa09a6](https://github.com/gohugoio/hugo/commit/f8b5fa09a6) \u2014 _Fix prevention of direct symlink reads in resources.Get_\n**Affected versions:** v0.123.0 through v0.161.1. Earlier versions are not affected.\n**Fixed in:** v0.162.0.\n**Severity:** Medium. Requires the attacker to be able to place (or convince a site author to place) a symlink inside a mounted directory \u2014 for example, inside a locally-vendored theme under `themes/`. Themes mounted as Go modules from GitHub have symlinks stripped on download and are not affected. Multi-directory walks (e.g. content/asset walking) were not affected either; only direct lookups via `resources.Get` followed symlinks.\n\n**Description.** Hugo\u0027s virtual filesystem is designed so that files under a mount cannot reach outside the mount tree. A regression introduced in v0.123.0 caused `RootMappingFs.statRoot` to call `Stat` (which follows symlinks) instead of `Lstat`, so a direct `resources.Get \"somefile\"` where `somefile` was a symlink pointing outside the mount would return the target\u0027s contents. This effectively let a symlink planted inside a theme or local mount read arbitrary files reachable to the user running `hugo`.\n\n**Mitigation.** v0.162.0 calls `LstatIfPossible` and rejects symlinked entries with `os.ErrNotExist`, matching the behaviour of pre-v0.123.0 releases and of the directory-walking code paths.",
  "id": "GHSA-fw87-fv5r-9fpw",
  "modified": "2026-06-16T20:12:34Z",
  "published": "2026-06-16T20:12:34Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/gohugoio/hugo/security/advisories/GHSA-fw87-fv5r-9fpw"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gohugoio/hugo/commit/f8b5fa09a64950c32b803821ede411ebfe772b7a"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/gohugoio/hugo"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gohugoio/hugo/releases/tag/v0.162.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Hugo: Symlink confinement bypass in resources.Get"
}



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