CVE-2026-0579: Critical GNU Wget2 Flaw Allows Remote Attackers to Overwrite Sensitive System Files

CVE OVERVIEW

CVE ID: CVE-2026-0579
Affected Software: GNU Wget2
CVSS v3.1 Score: 9.1 (Critical)
Severity: Critical
Attack Vector: Remote
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Exploitability: High
Exploit Availability: No public exploit released, but exploitation is practical and low-effort
Impact: Arbitrary file overwrite, potential persistence, credential compromise, denial of service, possible code execution
Attack Surface: File download handling and path resolution logic

VULNERABILITY DESCRIPTION

CVE-2026-0579 is a critical arbitrary file overwrite vulnerability in GNU Wget2 that occurs during file download operations when handling attacker-controlled remote content.

Due to insufficient validation of destination file paths, Wget2 can be tricked into writing downloaded data to arbitrary locations on the local file system. A remote attacker can abuse this behavior by crafting download responses or metadata that include path traversal sequences, absolute paths, or symbolic link abuse, causing Wget2 to overwrite sensitive files.

The vulnerability does not require authentication and only relies on convincing the victim (or an automated system) to download content using Wget2. The overwrite occurs silently and under the privileges of the user executing the command.

WHY THIS IS DANGEROUS

Wget2 is commonly used in:

Automation scripts
System update jobs
CI/CD pipelines
Container builds
Cron tasks

This makes CVE-2026-0579 especially dangerous because:

The tool is trusted
Downloads are often unattended
File writes are assumed safe
Compromise can go unnoticed

An attacker does not need to exploit memory corruption — file system access alone is enough to cause serious damage.

ATTACK SCENARIO (STEP-BY-STEP)

An attacker hosts a malicious file or response designed to manipulate the download destination.
The attacker convinces the victim or automation job to fetch the file using Wget2.
The crafted response causes Wget2 to resolve the output path incorrectly.
Wget2 overwrites a sensitive local file instead of saving to the intended directory.
The attacker gains one or more of the following:
- Persistent access
- Credential injection
- System disruption
- Execution of attacker-controlled scripts

FILES AT RISK

Depending on permissions, attackers may overwrite:

~/.ssh/authorized_keys
Shell startup files (.bashrc, .profile)
Application configuration files
Cron job definitions
Scripts executed by automation
Log files (to hide activity)
Any writable file within the user’s scope

Even non-root overwrites can result in long-term persistence or lateral movement.

MITRE MAPPING

CWE

CWE-22 – Improper Limitation of a Pathname to a Restricted Directory
CWE-73 – External Control of File Name or Path

MITRE ATT&CK TECHNIQUES

T1203 – Exploitation for Client Execution
T1105 – Ingress Tool Transfer
T1547 – Boot or Logon Autostart Execution
T1059 – Command and Scripting Interpreter (post-exploitation)

DETECTION STRATEGY

WHAT TO MONITOR

wget2 executions followed by file writes outside expected directories
Unexpected modifications to SSH keys, startup scripts, or configuration files
File changes occurring immediately after network downloads
Download activity from unusual or newly registered domains

LOG SOURCES TO USE

Linux auditd
EDR / XDR telemetry
File Integrity Monitoring (FIM)
Process execution logs
Network proxy or firewall logs
CI/CD pipeline logs

ORIGINAL DETECTION RULES

1. Auditd – Detect Sensitive File Writes by Wget2

auditctl -a always,exit -F exe=/usr/bin/wget2 -F perm=wa -S open,openat -k wget2_file_overwrite

Investigate events where the target file is outside known download paths.

2. Sigma – Suspicious Wget2 Download Behavior

title: GNU Wget2 Suspicious File Write
logsource:
  product: linux
  category: process_creation
detection:
  selection:
    Image|endswith: wget2
  condition: selection
level: high

Correlate with file write events within a short time window.

3. Behavioral Rule (EDR / SIEM)

Alert if:

wget2 is executed
AND a file is created or modified in:
- .ssh/
- /etc/
- user startup directories
WITHIN 300 seconds

4. OSQuery – Post-Download File Write Check

SELECT p.pid, p.cmdline, f.target_path
FROM processes p
JOIN file_events f ON p.pid = f.pid
WHERE p.cmdline LIKE '%wget2%'
AND f.target_path NOT LIKE '%Downloads%';

MITIGATION AND REMEDIATION

IMMEDIATE ACTIONS

Upgrade GNU Wget2 to the latest patched version
Audit systems for unexpected file modifications
Rotate credentials if SSH or auth files were modified
Review automation jobs using Wget2

TEMPORARY CONTROLS

Avoid running Wget2 with elevated privileges
Restrict file system write permissions
Run Wget2 inside containers or sandboxed environments
Validate download sources explicitly

OFFICIAL PATCH LINK

GNU Wget2 – Official Releases and Security Fixes
https://github.com/rockdaboot/wget2/releases

FINAL TAKEAWAY

CVE-2026-0579 turns a routine file download operation into a powerful attack primitive. By abusing how Wget2 handles download destinations, attackers can overwrite critical files without triggering alerts or crashes.

This vulnerability is especially dangerous in automated environments, where Wget2 runs silently and repeatedly. While no public exploit exists yet, the attack requires minimal effort and no special access.

Patch immediately, monitor aggressively, and treat unexpected Wget2 file writes as a potential compromise.