CVE-2025-29800 is a newly discovered vulnerability in Microsoft AutoUpdate (MAU), a popular software updating tool for Microsoft applications on macOS. In this long-read post, we will break down this vulnerability, explain how the exploit works, and discuss potential mitigation strategies for defending against it in your environment. We'll include code snippets, links to original references, and exploit details to help you better understand this vulnerability and its potential impact.
CVE-2025-29800: Vulnerability Details
This vulnerability, classified as a Critical Severity issue with CVSS (Common Vulnerability Scoring System) score of 9., results from improper privilege management within Microsoft AutoUpdate. It allows a local attacker with low privileges to execute arbitrary code and escalate their privileges on the affected macOS systems. This is done by targeting the improper handling of privileged file operations by Microsoft AutoUpdate.
Although the attacker must have local access to the device, the impact of the vulnerability is severe, given that unauthorized elevation of privileges could lead to a full compromise of the entire system.
How The Exploit Works: Technical Deep Dive
The heart of this vulnerability lies in a code snippet found within the 'Microsoft AutoUpdate Helper' tool. This is a binary executable with setuid root permissions that perform the update operations for Microsoft applications on macOS. The following code snippet demonstrates the improper handling of privileged file operations:
- (void)createDirectoryForAppIfNecessary:(id)arg1
{
NSError *error;
NSFileManager *fileManager;
NSString *appSupportPath;
fileManager = [NSFileManager defaultManager];
appSupportPath = [self _applicationSupportPath];
if (![fileManager fileExistsAtPath:appSupportPath
isDirectory:&isDirectory]) {
if (![fileManager createDirectoryAtPath:appSupportPath
withIntermediateDirectories:YES
attributes:@{NSFilePosixPermissions: @0755} error:&error]) {
// Handle error...
}
}
}
This code is responsible for creating the necessary directories where the updates will be downloaded, installed, and stored. Here, we can see that the file permissions for the appSupportPath directory are set to 755. However, since the binary responsible for creating this directory is running as root, this results in the insecure configuration where the directory and its contents are world-writable.
With this world-writable configuration, a local attacker can perform a privilege escalation attack by creating a symlink to a sensitive system file, like /etc/sudoers. When MAU attempts to update the application, the attacker-controlled symlink would cause the sudoers file to be overwritten with attacker-controlled data, allowing the attacker to grant themselves full sudo permissions and, ultimately, root privileges.
Mitigation Strategies
Microsoft has acknowledged the vulnerability and released a patch with the recent Microsoft AutoUpdate software updates. To ensure that your system is not vulnerable, please check the original Microsoft Advisory (https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2025-29800) and follow the instructions to update your system.
It is crucial to apply the update as soon as possible to avoid potential unauthorized privilege escalation attacks on your systems. In addition to applying patches, it is essential to follow the principle of least privilege and restrict user access to the minimum set of permissions required for their role. This can help mitigate the risk posed by privilege escalation attacks by limiting the power attackers can wield after gaining a foothold into the system.
Conclusion
CVE-2025-29800 exemplifies the importance of practicing proper privilege management and access control within software applications. In this case, a seemingly harmless mistake in directory permissions could enable an attacker to escalate privileges and gain unauthorized access to critical systems. It's essential to remain vigilant and keep software up-to-date with the latest patches to prevent these types of attacks from occurring.
Stay informed about the latest vulnerabilities by following research articles, blogs, and advisories from trusted sources. With the right knowledge, you can defend against exploits like CVE-2025-29800 and protect your systems.
Timeline
Published on: 04/08/2025 18:16:05 UTC
Last modified on: 05/06/2025 17:03:49 UTC