CVE-2014-8241 in TigerVNC
Summary
by MITRE
XRegion in TigerVNC allows remote VNC servers to cause a denial of service (NULL pointer dereference) by leveraging failure to check a malloc return value, a similar issue to CVE-2014-6052.
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Analysis
by VulDB Data Team • 10/08/2022
The vulnerability identified as CVE-2014-8241 affects the XRegion component within TigerVNC, a popular open-source implementation of the VNC protocol. This flaw represents a classic denial of service condition that can be exploited by remote VNC servers to disrupt service availability. The vulnerability stems from inadequate error handling during memory allocation operations, specifically when the malloc function fails to allocate memory. When malloc returns a NULL pointer due to insufficient memory resources, the application fails to properly validate this return value before proceeding with subsequent operations. This oversight creates a critical execution path where a NULL pointer dereference occurs, leading to application termination and complete service disruption for legitimate users. The flaw operates at the core level of memory management within the XRegion handling code, making it particularly dangerous as it can be triggered through normal VNC protocol communication.
The technical nature of this vulnerability aligns with CWE-476, which specifically addresses NULL pointer dereference conditions in software implementations. This weakness allows attackers to manipulate application behavior through memory allocation failures, creating a reliable vector for denial of service attacks. The vulnerability demonstrates poor defensive programming practices where developers failed to implement proper error checking mechanisms for dynamic memory allocation. In VNC environments, this issue becomes particularly problematic as remote attackers can leverage the protocol's design to send malformed region data that triggers the memory allocation failure. The similarity to CVE-2014-6052 indicates this represents a broader pattern of memory management flaws within the TigerVNC codebase, suggesting systematic weaknesses in the application's robustness against malformed input data.
From an operational perspective, this vulnerability significantly impacts the availability and reliability of VNC services deployed in enterprise environments. When exploited, the denial of service condition can affect remote desktop access for users, potentially disrupting critical business operations that depend on graphical desktop access. The attack requires minimal privileges as it can be executed by any remote VNC server attempting to establish connections, making it particularly dangerous in multi-tenant environments or public-facing VNC servers. Network administrators may experience service interruptions that are difficult to diagnose, as the application crash occurs during normal operation rather than during explicit malicious activity. The vulnerability essentially allows an attacker to remotely terminate legitimate VNC sessions and prevent authorized users from accessing their desktop environments, creating a persistent availability issue that can be repeatedly exploited until patched.
Mitigation strategies for CVE-2014-8241 should focus on immediate code-level fixes that implement proper error handling for memory allocation operations. The recommended approach involves adding explicit NULL pointer checks after malloc calls to ensure that memory allocation failures are properly handled before attempting to use the allocated memory. Organizations should prioritize updating to patched versions of TigerVNC that address this specific vulnerability, as the fix typically involves straightforward defensive programming improvements. Network-level mitigations can include implementing VNC server access controls, monitoring for unusual connection patterns, and deploying intrusion detection systems that can identify potential exploitation attempts. Additionally, system administrators should consider implementing redundant VNC services or alternative remote access solutions to maintain operational continuity during patch deployment. The vulnerability serves as a reminder of the critical importance of robust error handling in security-sensitive applications, particularly those handling network communications and user sessions.