CVE-2025-46836: net-tools Linux Utility RCE Vulnerability

CVE-2025-46836 Overview

CVE-2025-46836 is a stack-based buffer overflow vulnerability affecting net-tools, a foundational collection of network utility programs for Linux operating systems. The vulnerability exists in the get_name() function within interface.c, where interface labels from /proc/net/dev are copied into a fixed 16-byte stack buffer without proper bounds checking. This flaw can lead to arbitrary code execution or application crashes when processing maliciously crafted interface names.

Critical Impact

Local attackers can exploit this stack-based buffer overflow to potentially execute arbitrary code or cause denial of service on affected Linux systems running vulnerable versions of net-tools utilities such as ifconfig.

Affected Products

• net-tools versions up to and including 2.10
• Linux distributions shipping vulnerable net-tools packages
• Systems using ifconfig and related NET-3 networking utilities

Discovery Timeline

• 2025-05-14 - CVE CVE-2025-46836 published to NVD
• 2025-05-31 - Last updated in NVD database

Technical Details for CVE-2025-46836

Vulnerability Analysis

This vulnerability stems from improper input validation (CWE-20) in the get_name() function within the net-tools library. When Linux network utilities like ifconfig parse the /proc/net/dev file to enumerate network interfaces, the function reads interface labels and copies them into a fixed 16-byte stack buffer. The critical flaw is the absence of bounds checking during this copy operation—if an interface label exceeds the expected size, the function continues writing beyond the buffer boundary, corrupting adjacent stack memory.

The local attack vector means an attacker must have some level of access to the target system. While the vulnerability does not inherently provide privilege escalation, successful exploitation could result in arbitrary code execution within the context of the running process or cause the affected utility to crash, leading to denial of service.

Root Cause

The root cause is a classic stack-based buffer overflow resulting from insufficient bounds validation. The get_name() function in interface.c allocates a fixed 16-byte buffer (matching the IFNAMSIZ constant for interface names) on the stack but fails to enforce this limit when copying data from /proc/net/dev. The function iterates through characters without tracking the destination buffer's remaining capacity, enabling an overflow condition when processing unexpectedly long interface labels.

Attack Vector

The attack is local in nature, requiring an attacker to manipulate the contents of /proc/net/dev or create conditions where interface labels exceed the expected buffer size. An attacker with local access could potentially craft malicious network interface configurations or leverage other system components to inject oversized interface names. When a vulnerable net-tools utility (such as ifconfig) subsequently reads and parses the interface information, the buffer overflow is triggered.

The attack does not require elevated privileges to trigger but also does not directly provide privilege escalation. The primary impact is availability through crashes, with potential for code execution depending on stack layout and exploitation technique.

 }
 
 static const char *get_name(char *name, const char *p)
+/* Safe version — guarantees at most IFNAMSIZ‑1 bytes are copied
+   and the destination buffer is always NUL‑terminated.             */
 {
-    while (isspace(*p))
-	p++;
-    while (*p) {
-	if (isspace(*p))
-	    break;
-	if (*p == ':') {	/* could be an alias */
-		const char *dot = p++;
- 		while (*p && isdigit(*p)) p++;
-		if (*p == ':') {
-			/* Yes it is, backup and copy it. */
-			p = dot;
-			*name++ = *p++;
-			while (*p && isdigit(*p)) {
-				*name++ = *p++;
-			}
-		} else {
-			/* No, it isn't */
-			p = dot;
-	    }
-	    p++;
-	    break;
-	}
-	*name++ = *p++;
+    char       *dst = name;                 /* current write ptr          */

Source: GitHub Commit Update

The patch introduces bounds checking by tracking the destination pointer and ensuring no more than IFNAMSIZ-1 bytes are copied, with proper NUL termination guaranteed.

Detection Methods for CVE-2025-46836

Indicators of Compromise

• Unexpected crashes of ifconfig or other net-tools utilities during execution
• Core dumps or segmentation faults when running network interface enumeration commands
• Unusual entries or malformed interface names in /proc/net/dev
• Stack corruption or memory access violation errors in system logs

Detection Strategies

• Monitor system logs for segmentation faults or crashes related to ifconfig, netstat, or other net-tools binaries
• Implement file integrity monitoring on net-tools binaries to detect unauthorized modifications
• Use application crash monitoring to identify repeated failures of network utilities
• Deploy runtime protection solutions that detect stack buffer overflow attempts

Monitoring Recommendations

• Enable crash reporting and core dump analysis for net-tools utilities
• Monitor /var/log/syslog and /var/log/messages for segmentation fault entries from network utilities
• Implement security scanning to identify systems running vulnerable net-tools versions (2.10 and earlier)
• Track package versions across infrastructure to identify systems requiring updates

How to Mitigate CVE-2025-46836

Immediate Actions Required

• Update net-tools to version 2.20 or later when available from your distribution
• Apply vendor-provided security patches from your Linux distribution's package repository
• Consider using alternative network utilities such as ip from iproute2 as a temporary measure
• Restrict local access to affected systems where practical

Patch Information

A security patch has been released and is expected to be included in net-tools version 2.20. The patch modifies the get_name() function in lib/interface.c to implement proper bounds checking, ensuring that at most IFNAMSIZ-1 bytes are copied and the destination buffer is always properly NUL-terminated. The fix is available via GitHub commit 7a8f42fb20013a1493d8cae1c43436f85e656f2d. Debian users should refer to the Debian LTS announcement for distribution-specific updates.

Workarounds

• Use ip command from the iproute2 package as a replacement for ifconfig and related net-tools utilities
• Limit local user access to systems running vulnerable versions until patches can be applied
• Monitor for abnormal interface name entries that could trigger the overflow condition
• Consider compiling net-tools from source with the security patch applied if distribution packages are not yet updated

# Configuration example
# Check current net-tools version
ifconfig --version 2>&1 | head -1

# Update net-tools on Debian/Ubuntu systems
sudo apt update && sudo apt upgrade net-tools

# Alternative: Use iproute2 commands instead of net-tools
# Replace 'ifconfig' with 'ip addr'
ip addr show

# Replace 'netstat' with 'ss'
ss -tulpn