On June 6, 2024, CVE-2024-53589 was published, revealing a buffer overflow vulnerability in the GNU objdump 2.43 utility. This flaw lies deep in the BFD (Binary File Descriptor) library, specifically within how the library deals with TEKHEX format files. In this post, we’ll break down what the problem is, how exploitation works, and why this matters to anyone working with objdump or TEKHEX files. We'll also share references and a demonstrative code snipplet.

🔎 Understanding the Background

objdump is an important tool for inspecting compiled binaries. It’s bundled with GNU's binutils—which means it’s widely used by developers, reverse engineers, and even automation pipelines.

The BFD library is core to binutils, providing abstraction for various binary formats—like ELF, PE/COFF, and more obscure ones like TEKHEX, which is a HEX object file format used by old Tektronix development systems.

What is TEKHEX?

It's an old ASCII encoding method for object files, little used now—but still part of GNU's broad compatibility.

🛠 Vulnerability Deep Dive

Affected Version: Binutils 2.43 (and possibly prior)
Component: libbfd (bfd), particularly TEKHEX file parsing

The problem occurs in code that reads in TEKHEX records and processes them (including addresses and data fields). There’s insufficient checks on buffer sizes when copying input data fields, allowing crafted files to overwrite adjacent memory.

In-Depth: Where’s the Overflow?

Examining the vulnerability from the patch diff and CVE details, it happens here:

/* Simplified view of the vulnerable code in bfd/tekhex.c */

char buffer[TEKHEX_RECORD_MAX_LEN];
...

while (fgets(buffer, sizeof(buffer), input_file))
{
    // parse different fields
    sscanf(buffer + offset, "%s", parsed_field);
    // ... flawed length checking
}

The real code uses insufficient bounds checking during record parsing, potentially allowing overwrites if an attacker crafts overlong lines.

Who is vulnerable?

Anyone using GNU objdump/binutils 2.43 (or tools based on its BFD lib) to analyze untrusted TEKHEX files.

What could happen?

A malicious TEKHEX file can trigger a buffer overflow, leading to crashes (“Denial of Service”), or—*on some systems, and with careful crafting—potentially arbitrary code execution.*

How could attackers use this?

- Trick a user/developer/automated script into running objdump -D (or similar) on a malicious TEKHEX file.
- Upon parsing, attacker-set input overflows the stack or heap, potentially letting attacker control instruction flow.

💻 Proof-of-Concept Exploit

Here’s a minimal TEKHEX file (crafted for demonstration) and how you would trigger the bug against objdump 2.43:

Save this as evil.tekhex

:%99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999

This overly long record is way above legitimate TEKHEX line lengths.

Trigger the Overflow

objdump -D evil.tekhex

On the vulnerable version, you’ll see a crash, e.g.

Segmentation fault (core dumped)

For a full proof-of-concept, a researcher may use AddressSanitizer (ASAN) to spot out-of-bounds reads/writes and other memory errors when running this code.

📚 References

- CVE-2024-53589 NVD Entry
- Sourceware Security Advisory
- Official Binutils Patch Commit
- Binutils Bug List: TEKHEX Security Fix

🛡️ Mitigation

- Update binutils to 2.44 or later, or apply the patch above.
- Never run objdump or similar tools on TEKHEX files from unknown/untrusted sources.

📝 Conclusion

CVE-2024-53589 is another example of how even legacy file handlers can introduce modern buffer overflow risks, especially in widely distributed, older C codebases like binutils. While TEKHEX may be obscure, the sheer reach of objdump makes this bug a notable risk in automated build and analysis environments.
Stay patched, stay cautious, and when in doubt—don't objdump that weird HEX file from the internet.


*Written exclusively for you. For more analysis, bookmark this post and follow updates from security maintainers and sourceware.org.*


If you have questions or want more technical details, comment below or see the sources above for in-depth code and commits!

Timeline

Published on: 12/05/2024 20:15:22 UTC
Last modified on: 12/11/2024 17:15:20 UTC