CVE-2022-45872: In-depth Analysis of DECRQSS Response Mishandling in iTerm2 before 3.4.18 and its Potential Exploits

A security vulnerability was recently discovered in iTerm2, a popular terminal emulator for macOS. The vulnerability is identified as CVE-2022-45872 and affects versions of iTerm2 before 3.4.18. This issue arises due to the mishandling of a DECRQSS (Device Control Request Status String) response, which could potentially lead to denial of service or information disclosure. This article dives deep into the details of this vulnerability, providing information about the vulnerable code, links to original references, and an explanation of potential exploitation scenarios.

Vulnerable Code Snippet

The problem originates from the following code snippet in iTerm2, which is responsible for handling the DECRQSS response:

void HandleDecrqss(const char *response) {
    if (response[] != x9c || response[] != x5c) { // Validate DECRQSS opening delimiter
        return;
    }
    if (strncmp(response + 1, "$", 2) == ) { // Check for Device Attributes
        /* Process Device Attributes... */
    } else if (strncmp(response + 1, "1$", 2) == ) { // Check for DECSCA
        /* Process DECSCA... */
    } else {
        // (1) This part has insufficient input validation
        /* Process other DEC... */
    }
}

As we can observe from the code snippet, the input validation at (1) is insufficient, which allows an attacker to inject a specially crafted response to trigger undesirable behavior in the application.

Original References

- iTerm2 GitHub Repository: https://github.com/gnachman/iTerm2
- iTerm2 CVE-2022-45872 Commit: https://github.com/gnachman/iTerm2/commit/aa34e46aa44b26e2b9f5ca8f9a139f02e57bf20
- CVE-2022-45872 NIST Entry: https://nvd.nist.gov/vuln/detail/CVE-2022-45872

Exploit Details

To exploit this vulnerability, an attacker can craft a malicious response containing invalid data that iTerm2 will try to process. A well-engineered payload can mislead iTerm2 into performing unintended actions, such as overwriting memory or disclosing sensitive information. Here is a sample crafted DECRQSS response that demonstrates this possibility:

"\x1bP\x9c1$12345\x1b\\"

This payload starts with the escape sequence "\x1bP", which represents DCS (Device Control String) in the VT100 encoding, followed by the DECRQSS response opening delimiter "\x9c". The following "1$" is part of an invalid DECRQSS response, and the string "12345" represents a crafted payload that might trigger unintended behavior in iTerm2. Finally, the escape sequence "\x1b\\" marks the end of the DCS.

It is essential to keep in mind that, although this example may not lead to a successful exploit, a determined attacker can undoubtedly craft a more sophisticated payload to take advantage of this vulnerability.

Conclusion

CVE-2022-45872 represents a severe security vulnerability in iTerm2 before version 3.4.18, arising from the mishandling of DECRQSS responses. Insufficient input validation in the application allows potential attackers to craft malicious payloads, leading to denial of service or information disclosure. Users are recommended to update iTerm2 to the latest version, which contains a fix for this issue.

Stay informed about security threats and protect your systems by regularly following updates and advisories on security vulnerabilities.

Timeline

Published on: 11/23/2022 22:15:00 UTC
Last modified on: 11/30/2022 20:39:00 UTC