CVE-2026-40489: editorconfig-core-c Buffer Overflow Flaw

CVE-2026-40489 Overview

A stack-based buffer overflow vulnerability exists in the ec_glob() function of editorconfig-core-c, a core library used by plugins supporting EditorConfig parsing. This vulnerability allows an attacker to crash any application using libeditorconfig by providing a specially crafted directory structure and .editorconfig file. This issue represents an incomplete fix for CVE-2023-0341, where the pcre_str buffer was protected in version 0.12.6, but the adjacent l_pattern[8194] stack buffer did not receive equivalent protection.

Critical Impact

Attackers can trigger a denial of service condition in any application that parses EditorConfig files by exploiting the unprotected l_pattern stack buffer, potentially crashing development tools, text editors, and IDEs that rely on libeditorconfig.

Affected Products

• editorconfig-core-c versions up to and including 0.12.10
• Applications and plugins using libeditorconfig for EditorConfig parsing
• Development environments and text editors with EditorConfig support

Discovery Timeline

• April 18, 2026 - CVE-2026-40489 published to NVD
• April 20, 2026 - Last updated in NVD database

Technical Details for CVE-2026-40489

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow) and stems from an incomplete security fix applied in version 0.12.6. The original vulnerability (CVE-2023-0341) addressed a buffer overflow in the pcre_str buffer within the ec_glob() function. However, the adjacent stack buffer l_pattern[8194] was left unprotected, creating a secondary attack vector.

The vulnerability requires local access and can be triggered without user interaction. When exploited, the overflow can corrupt stack memory, leading to application crashes. On systems with modern compiler protections like Ubuntu 24.04's FORTIFY_SOURCE, the overflow is converted to a SIGABRT signal, resulting in a denial of service condition rather than potential code execution.

Root Cause

The root cause lies in the use of strcpy() to copy pattern data into the fixed-size l_pattern[8194] stack buffer without proper bounds checking. While the previous fix protected the pcre_str buffer from overflow, it failed to apply equivalent protections to the l_pattern buffer, leaving it vulnerable to oversized input patterns supplied through maliciously crafted .editorconfig files.

Attack Vector

An attacker with local access can exploit this vulnerability by creating a specially crafted directory structure containing an .editorconfig file with an excessively long pattern string. When an application using libeditorconfig parses this malicious configuration, the ec_glob() function copies the pattern into the l_pattern stack buffer without validating its length, causing a stack-based buffer overflow. This can crash the target application, resulting in denial of service.

     _Bool                     are_braces_paired = 1;
     UT_array *                nums;     /* number ranges */
     int                       ret = 0;
+    size_t                    pattern_len = strlen(pattern);
 
-    strcpy(l_pattern, pattern);
+    /* Reject patterns that would overflow l_pattern in the copy below. */
+    if (pattern_len >= sizeof(l_pattern))
+        return -1;
+    memcpy(l_pattern, pattern, pattern_len + 1);
     p_pcre = pcre_str + 1;
     pcre_str_end = pcre_str + 2 * PATTERN_MAX;
 

Source: GitHub Commit Update

Detection Methods for CVE-2026-40489

Indicators of Compromise

• Unexpected SIGABRT crashes in applications using libeditorconfig
• Presence of unusually large pattern strings in .editorconfig files
• Application crash logs indicating stack corruption in ec_glob() or related functions
• Suspicious .editorconfig files with pattern lengths exceeding 8194 characters

Detection Strategies

• Monitor for abnormal application terminations in EditorConfig-enabled tools and IDEs
• Implement file integrity monitoring for .editorconfig files in project directories
• Deploy static analysis tools to detect oversized pattern strings in EditorConfig files
• Review system logs for SIGABRT signals originating from applications linked against libeditorconfig

Monitoring Recommendations

• Enable core dump collection to capture crash context for forensic analysis
• Configure application crash monitoring for development tools and text editors
• Implement alerts for repeated crashes in EditorConfig-parsing applications
• Monitor for creation or modification of .editorconfig files with anomalous sizes

How to Mitigate CVE-2026-40489

Immediate Actions Required

• Upgrade editorconfig-core-c to version 0.12.11 or later immediately
• Rebuild any applications statically linked against affected versions of libeditorconfig
• Review and validate .editorconfig files in project repositories for suspicious content
• Consider temporarily removing EditorConfig support if immediate patching is not feasible

Patch Information

The security fix has been released in editorconfig-core-c version 0.12.11. The patch adds proper bounds checking before copying pattern data into the l_pattern buffer, rejecting patterns that would exceed the buffer size. The fix replaces the unsafe strcpy() call with a length-validated memcpy() operation. The patch is available through the GitHub Release v0.12.11, and detailed information is provided in the GitHub Security Advisory GHSA-97xg-vrcq-254h.

Workarounds

• Validate .editorconfig files before use, rejecting those with patterns exceeding 8000 characters
• Compile applications with FORTIFY_SOURCE enabled to convert potential exploits to controlled crashes
• Restrict write access to directories containing .editorconfig files
• Use containerization or sandboxing for applications processing untrusted EditorConfig files

# Configuration example
# Check editorconfig-core-c version and upgrade
pkg-config --modversion editorconfig

# On Debian/Ubuntu systems, update to patched version
sudo apt update && sudo apt upgrade libeditorconfig0

# Verify the installed version includes the fix
dpkg -l | grep editorconfig