CVE-2024-29748 - How a Simple Logic Bug Can Let Local Users Escalate Privileges
In early 2024, security researchers unearthed a critical vulnerability, CVE-2024-29748. This bug may not sound glamorous: it’s a logic error buried in a common piece of code found in many Linux-based systems. But its impact is serious—a regular user could climb the privilege ladder to gain unintended access. In this post, we’ll break down how this bug works, show you sample code, and walk you through how it can be exploited.
What is CVE-2024-29748?
Let’s start simple. CVE-2024-29748 is a vulnerability where a mistake in how the program checks user requests allows a normal, unprivileged user to perform actions as administrator, or root, when they shouldn’t.
This happens locally—meaning the attacker needs to already have access to the computer (for instance, as a regular user). The user has to trigger the bug by interacting with the system, but they don’t need fancy hacking skills to do it.
What Causes the Vulnerability?
The root of the problem is in a function that is supposed to check whether a user has permission to perform a certain action. Instead, due to a logic slip, it sometimes lets them through even when it shouldn’t.
Here’s a sample of what this buggy logic can look like (note: this is a simplification, not the actual vulnerable file):
// Vulnerable logic in CVE-2024-29748
int check_user_permission(uid_t user) {
if (user == || user == current_user) {
// Allow the action for root or current user
return 1;
}
// Should deny everyone else
return ;
}
But somewhere else, the code mixes up which uid to check, or doesn’t correctly re-verify after a user interacts with the program (like entering a password or clicking an "OK" button).
A local user can then trick the program by causing a situation where their user ID is considered valid, even without privileges.
Attacker logs in as a regular user, say guest, on a vulnerable Linux system.
2. The attacker opens the affected tool or service, which prompts for a sensitive operation (for example, changing a system config).
3. Instead of stopping the user, due to the logic flaw, the program’s check sees the request as coming from a valid user (sometimes due to a race condition or mishandled variable), and allows the action.
A simplified proof-of-concept (POC) could look like this in a shell
# Assume 'vuln_tool' has the buggy logic
./vuln_tool --set-admin-config
echo "Exploit succeeded: configuration changed as unprivileged user."
In reality, exploiting this may need some timing or scripting based on the actual vulnerability, but you get the idea.
User Interaction Required:
This isn’t a remote attack—*someone has to be at the keyboard.* They may have to click a button or run a command themselves to trigger the bug.
Why Does This Matter?
- No extra permissions needed: The attacker doesn’t need to be in a special group or already have high rights.
Are You at Risk?
You might be, if you're running an affected version of the software. Look for security advisories from your Linux vendor or maintainer. Update as soon as you can.
References and More Reading
- NVD Entry, CVE-2024-29748
- Security Advisory from the Vendor (example link)
- Original researcher write-up
- OWASP: What is a Local Privilege Escalation?
For a technical deep dive (where available):
Conclusion
CVE-2024-29748 is a reminder: a single line of bad logic can blow a hole in your system’s defense. If you’re an admin, check your patches. If you’re a developer, review your permission checks. Always ask: “Does this code *really* stop what it’s supposed to stop?”
Stay safe and stay updated!
*This post is for educational purposes and does not provide actual exploit code.*
Timeline
Published on: 04/05/2024 20:15:08 UTC
Last modified on: 04/08/2024 22:52:33 UTC