CVE-2025-5278: GNU Coreutils Buffer Overflow Vulnerability

CVE-2025-5278 Overview

A heap buffer under-read vulnerability has been discovered in the GNU Coreutils sort utility. The flaw resides in the begfield() function, which improperly handles memory boundaries when processing commands that use the traditional key format. When a user runs a crafted command exploiting this vulnerability, the program may access memory outside the allocated buffer, potentially leading to application crashes or the leakage of sensitive data from memory.

Critical Impact

Local attackers can craft malicious input to the sort utility that causes memory under-read, potentially exposing sensitive data from adjacent memory regions or causing denial of service through application crashes.

Affected Products

• GNU Coreutils (versions prior to the security fix)
• Linux distributions shipping vulnerable Coreutils packages
• Systems using the sort utility with traditional key format options

Discovery Timeline

• May 27, 2025 - CVE-2025-5278 published to NVD
• October 22, 2025 - Last updated in NVD database

Technical Details for CVE-2025-5278

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), though the actual memory corruption occurs as a heap buffer under-read in the begfield() function within the sort utility. The flaw manifests when the program processes input using the traditional key format specification, causing it to read memory before the start of the allocated buffer.

The local attack vector requires user interaction, as the victim must execute a crafted sort command. While this limits the attack surface, the vulnerability can be exploited in scenarios where untrusted input is processed through shell scripts or automated pipelines that invoke the sort command with user-controlled parameters.

The impact includes potential information disclosure through memory leakage and denial of service via application crashes. The confidentiality and availability impacts are limited in scope, affecting only the local system context.

Root Cause

The root cause lies in improper bounds checking within the begfield() function of the GNU Coreutils sort utility. When parsing field specifications using the traditional key format (e.g., +POS1 -POS2), the function fails to properly validate input boundaries before accessing memory. This allows the program to read memory locations before the start of the intended buffer, constituting a heap buffer under-read condition.

Attack Vector

The vulnerability requires local access and user interaction to exploit. An attacker must craft a malicious command using the sort utility's traditional key format options. The attack vector involves:

1. Creating a specially crafted input file or command-line argument
2. Invoking the sort utility with traditional key format parameters that trigger the vulnerable code path in begfield()
3. The under-read condition occurs during field parsing, potentially leaking memory contents or causing a crash

The traditional key format uses positional notation (e.g., sort +1 -2) rather than the modern -k option format. Exploiting this requires specific knowledge of the vulnerable parsing behavior and construction of inputs that trigger the boundary violation.

Detection Methods for CVE-2025-5278

Indicators of Compromise

• Unexpected crashes or segmentation faults in the sort utility during normal operations
• Unusual command-line invocations of sort using traditional key format syntax (+POS -POS)
• Memory-related errors in system logs associated with Coreutils processes
• Automated scripts or cron jobs processing untrusted input through the sort command

Detection Strategies

• Monitor for abnormal sort process terminations with memory-related exit codes
• Implement system call auditing to detect suspicious sort invocations with traditional key format arguments
• Deploy runtime memory protection tools (ASAN, Valgrind) in testing environments to catch under-read conditions
• Review shell scripts and automation workflows for potentially vulnerable sort command usage patterns

Monitoring Recommendations

• Enable core dump collection for Coreutils utilities to aid in post-incident analysis
• Configure application-level logging for systems processing untrusted data through sorting operations
• Implement file integrity monitoring on Coreutils binaries to detect unauthorized modifications
• Set up alerting for repeated sort utility crashes that may indicate exploitation attempts

How to Mitigate CVE-2025-5278

Immediate Actions Required

• Update GNU Coreutils to the patched version containing commit 8c9602e3a145e9596dc1a63c6ed67865814b6633
• Review and update shell scripts to use modern -k option syntax instead of traditional key format
• Audit systems for automated processes that invoke sort with untrusted input
• Apply vendor-specific patches from your Linux distribution's security repository

Patch Information

The GNU Coreutils project has addressed this vulnerability in commit 8c9602e3a145e9596dc1a63c6ed67865814b6633. The fix corrects the boundary checking in the begfield() function to prevent under-read conditions when processing traditional key format specifications.

For patch details and the specific code changes, refer to the GNU Coreutils Commit Details. Distribution-specific patches are available through Red Hat CVE-2025-5278 Advisory and the Debian Security Tracker CVE-2025-5278.

Workarounds

• Migrate scripts from traditional key format (+POS -POS) to modern -k option syntax which uses different code paths
• Implement input validation and sanitization for any data processed through the sort utility
• Use containerization or sandboxing for processes that must handle untrusted input through Coreutils
• Consider alternative sorting implementations for security-critical applications until patches are applied

# Example: Converting traditional key format to modern syntax
# Vulnerable traditional format:
# sort +1 -2 input.txt

# Recommended modern format (use this instead):
sort -k 2,2 input.txt

# Verify installed Coreutils version:
sort --version