CVE-2008-5744 in Zaptel
Summary
by MITRE
Array index error in the dahdi/tor2.c driver in Zaptel (aka DAHDI) 1.4.11 and earlier allows local users in the dialout group to overwrite an integer value in kernel memory by writing to /dev/zap/ctl, related to an incorrect tor2 patch for CVE-2008-5396 that uses the wrong variable in a range check against the value of lc->sync.
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Analysis
by VulDB Data Team • 05/15/2025
The vulnerability described in CVE-2008-5744 represents a critical array index error within the DAHDI (Digium Asterisk Hardware Driver Interface) kernel module, specifically in the dahdi/tor2.c driver component. This flaw exists in Zaptel versions 1.4.11 and earlier, which are widely used in telephony systems for handling hardware interfaces. The vulnerability manifests when local users who belong to the dialout group attempt to write to the /dev/zap/ctl device file, creating a potential pathway for kernel memory corruption. The root cause stems from an incorrect patch implementation for CVE-2008-5396, where developers mistakenly referenced the wrong variable during a range check operation, specifically using lc->sync instead of the appropriate variable for validation purposes. This error creates a condition where an integer value in kernel memory gets overwritten, fundamentally compromising system stability and security.
The technical execution of this vulnerability involves a specific sequence of operations that exploit the flawed range checking logic. When a malicious user writes to the /dev/zap/ctl device, the system processes this input through the tor2.c driver without proper validation of the data being written. The incorrect implementation of the range check means that the validation against lc->sync fails to properly constrain the input values, allowing for out-of-bounds memory access. This type of vulnerability falls under the CWE-129 weakness category, which specifically addresses improper validation of array indices or other forms of bounds checking. The vulnerability represents a classic case of integer overflow or underflow conditions that can lead to memory corruption, making it particularly dangerous in kernel space where such errors can result in complete system compromise.
The operational impact of CVE-2008-5744 extends beyond simple memory corruption, as it provides a potential pathway for privilege escalation within systems running vulnerable Zaptel implementations. Local users who have membership in the dialout group can leverage this vulnerability to overwrite critical kernel memory locations, potentially allowing them to modify system behavior or even execute arbitrary code with kernel privileges. This represents a significant security risk for telephony systems that rely on DAHDI drivers, particularly in enterprise environments where such systems may be exposed to untrusted local users. The vulnerability's impact is further amplified by the fact that it affects the kernel driver level, meaning that successful exploitation could lead to complete system compromise, data loss, or service disruption. Organizations using these telephony systems face potential threats including unauthorized access to communication channels, system instability, and possible data exfiltration through kernel-level manipulation.
Mitigation strategies for this vulnerability require immediate patching of affected systems with updated Zaptel versions that contain proper implementation of the range checking logic. System administrators should also implement strict access controls to limit membership in the dialout group and restrict write access to /dev/zap/ctl device files. The remediation process involves not only applying the official patches but also conducting thorough system audits to identify any potential exploitation attempts. Additionally, organizations should consider implementing monitoring solutions that can detect anomalous writes to kernel device files, as this vulnerability could be exploited as part of broader attack campaigns targeting telephony infrastructure. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting kernel-level privilege escalation methods that leverage driver flaws to gain unauthorized system access. Given the nature of this vulnerability, it is essential for organizations to perform comprehensive security assessments of their telephony infrastructure and ensure that all kernel modules are kept up to date with the latest security patches.