CVE-2012-3368

Vulnerability

In dtach version 0.8, the attach.c file contains an integer signedness error. The return value of the read() system call is stored in an unsigned variable. When read() returns a negative value (e.g., -1 on error), the check for <= 0 fails because the negative value is interpreted as a large positive value when assigned to an unsigned type. This causes the code to incorrectly construct and send a packet with a length field set to 0xFF (255) instead of aborting the connection [1][3][4].

Exploitation

An attacker who can cause an unclean client disconnect (for example, by forcefully terminating a network session or causing an I/O error) can exploit this vulnerability. No authentication is required; the attacker only needs to be a client that can establish and then abruptly drop the connection. When the server processes the error condition from read(), it sends a crafted packet containing arbitrary stack memory data to the client. The bug is triggered in opportunistic circumstances, meaning the exact data leaked depends on the daemon's stack state at the time of the error [2][3].

Impact

A remote, unauthenticated attacker can obtain sensitive information from the dtach daemon's stack memory. This may include portions of memory that could contain credentials, private data, or other secrets. The disclosure occurs when the attacker reads the application data (e.g., an IRC client session) after the improper close. The initial disclosure is limited to the stack contents at the time of the failed read, but the attacker may be able to repeatedly trigger the condition to gather more information [2].

Mitigation

A patch was proposed in the upstream dtach bug tracker (SourceForge ticket #10) and attached to Red Hat Bugzilla bug 812551 [1][4]. The fix corrects the signedness error by properly handling negative return values from read(). Red Hat's security response team marked this issue as WONTFIX for certain Fedora versions, indicating that users should update to a fixed version of dtach once available or apply the provided patch manually. No CVE record indicates inclusion in the Known Exploited Vulnerabilities (KEV) catalog [2]. The recommended action is to upgrade to a version that contains the fix or to apply the patch from reference [4].