CVE-2024-40897 - Critical Stack Buffer Overflow in ORC < .4.39 Can Lead to Remote Code Execution

A serious security vulnerability has been discovered in the ORC (Oil Runtime Compiler) project, tracked as CVE-2024-40897. This flaw is a stack-based buffer overflow found in the orcparse.c source file of all ORC versions before .4.39. If a developer or CI system is tricked into processing a malicious input file—such as a poisoned .orc file—this bug could allow a remote attacker to execute arbitrary code on the build environment.

In this post, we'll walk through the detail of the bug, include code snippets showing the vulnerable code, outline how an exploit might work, and wrap up with references and remediation tips. If you use ORC in your build systems, update immediately!

What is ORC?

ORC is a library and compiler for vectorized code generation, used in projects like GStreamer and multimedia libraries. It processes scripts to generate C code or machine code optimized for SIMD architectures. Since it is often run automatically within developer environments or CI systems, it presents a prime target for supply chain attacks.

Vulnerability Breakdown

Stack-based buffer overflow bugs allow data to overwrite parts of the stack, potentially gaining control of the application flow.

In ORC versions prior to .4.39, the vulnerable code resides in orcparse.c and is triggered during the parsing phases when reading in ORC scripts.

Vulnerable Code Snippet

The bug centers around improper array bounds checking when reading tokens from an input file. Here’s an abstracted snippet (not the full code):

// orcparse.c: Simplified portrayal of the bug

#define MAX_TOKEN_LEN 256

char token[MAX_TOKEN_LEN];

// vulnerable function
void read_token(FILE *fp) {
    int i = ;
    int ch;
    while ((ch = fgetc(fp)) != EOF && ch != '\n') {
        token[i++] = ch;  // No check on i! Dangerous!
    }
    token[i] = ;
}

In this code, when a crafted file feeds a line longer than MAX_TOKEN_LEN, the character reading loop will overwrite the buffer, smashing the stack.

In the real code

If the attacker's file purposely feeds a huge token, the token array overflows.

How Could An Exploit Happen?

Imagine a targeted attacker submits a PR or build file with a malicious .orc script into a CI pipeline, or tricks a developer into building a third-party module. When ORC reads the malicious file:

The large, crafted token overflows the stack buffer.

2. Carefully crafted input can place shellcode (“payload”) on the stack and overwrite the return address.

Return execution flows to the attacker’s code.

Typical payloads for CI/CD attacks include remote reverse shells, data exfiltration scripts, or even ransomware droppers.

Example Malicious File

// This is not real ORC syntax, but shows the exploit idea
AAAA....(300 'A's)...[payload shellcode]

Original Source & References

- Official CVE-2024-40897 entry (NVD)
- ORC Project Homepage
- Upstream Patch Commit for ORC .4.39 *(placeholder, replace 'XYZ' with actual commit hash when available)*

The ORC team released version .4.39, which addresses this bug by adding proper bounds checking

void read_token(FILE *fp) {
    int i = ;
    int ch;
    while ((ch = fgetc(fp)) != EOF && ch != '\n') {
        if (i < MAX_TOKEN_LEN - 1) {  // Bounds check to prevent overflow
            token[i++] = ch;
        }
    }
    token[i] = ;
}

Avoid running untrusted code with high privileges during builds.

- Monitor CI/CD systems for abnormal activity.

Conclusion

CVE-2024-40897 is a critical supply-chain risk for anyone running vulnerable versions of ORC, especially in automatic build environments. Left unpatched, it could allow attackers to hijack developer systems or poison entire CI/CD pipelines via a simple file upload.

Don’t delay—patch now, and audit your pipeline security!

*This write-up is originally composed by our team, and aims for clarity and directness to help all devs stay secure.*

Timeline

Published on: 07/26/2024 06:15:02 UTC
Last modified on: 08/27/2024 13:52:53 UTC