CVE-2011-4073 in Openswan
Summary
by MITRE
Use-after-free vulnerability in the cryptographic helper handler functionality in Openswan 2.3.0 through 2.6.36 allows remote authenticated users to cause a denial of service (pluto IKE daemon crash) via vectors related to the (1) quick_outI1_continue and (2) quick_outI1 functions.
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Analysis
by VulDB Data Team • 01/05/2025
The CVE-2011-4073 vulnerability represents a critical use-after-free condition within the cryptographic helper handler functionality of Openswan versions 2.3.0 through 2.6.36. This flaw exists in the pluto IKE daemon which serves as the core component responsible for managing Internet Key Exchange protocol operations in Openswan implementations. The vulnerability specifically manifests in two distinct functions: quick_outI1_continue and quick_outI1, both of which handle the initial phase of IKE negotiation processes. The flaw arises from improper memory management where freed memory blocks are accessed after being deallocated, creating a scenario where subsequent operations attempt to reference already released memory locations. This type of vulnerability falls under CWE-416, which categorizes use-after-free conditions as a fundamental memory safety issue that can lead to system instability and potential exploitation. The vulnerability is particularly concerning because it affects the core cryptographic operations that secure network communications through IPsec tunnels.
The technical exploitation of this vulnerability requires an authenticated remote attacker who can establish a connection to the target system and manipulate the IKE negotiation process. When the pluto daemon processes certain IKE messages through the affected functions, it fails to properly validate memory references after deallocation occurs during the cryptographic helper processing. The quick_outI1_continue and quick_outI1 functions are responsible for handling the first message of the quick mode IKE exchange, where the daemon prepares and sends initial cryptographic parameters. During this process, the daemon allocates memory for cryptographic helper structures, processes them, and subsequently frees the memory. However, the flaw allows for a race condition or improper state management where the freed memory is accessed again, leading to undefined behavior. This memory corruption directly impacts the daemon's ability to maintain stable operation, ultimately causing the pluto IKE daemon to crash and terminate unexpectedly.
The operational impact of this vulnerability extends beyond simple denial of service as it fundamentally compromises the availability of secure communication channels that rely on Openswan for IPsec protection. When the pluto daemon crashes, all active IPsec tunnels that depend on that daemon become unavailable, disrupting network connectivity for all services relying on those secure connections. This creates cascading effects throughout the network infrastructure, particularly in environments where Openswan serves as the primary IPsec implementation for site-to-site connections, remote access VPNs, or secure inter-domain communications. The vulnerability affects organizations using various network security configurations including enterprise networks, cloud deployments, and government communications systems that depend on Openswan for secure network interconnectivity. The crash behavior can be particularly disruptive in mission-critical environments where continuous availability is essential, as the daemon restarts automatically but during this period all IPsec communications are suspended, creating potential security gaps and service interruptions.
Mitigation strategies for CVE-2011-4073 should prioritize immediate patching of affected Openswan installations to versions that contain the memory management fixes for the cryptographic helper functions. Organizations should implement network segmentation to limit the attack surface and reduce the impact of potential exploitation attempts. Monitoring systems should be enhanced to detect abnormal daemon crashes or restart patterns that may indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1499 which covers network denial of service attacks, and specifically targets the persistence and availability aspects of network security infrastructure. Additional defensive measures include implementing strict access controls to limit authentication to only authorized entities, as the vulnerability requires authentication to exploit. Network administrators should also consider deploying intrusion detection systems that can monitor for suspicious IKE protocol patterns that might indicate exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to identify any remaining unpatched systems within the network infrastructure, as the use-after-free condition could potentially be extended to more severe exploitation scenarios if combined with other vulnerabilities. The fix implemented in patched versions addresses the root cause by ensuring proper memory management and validation of helper function states during cryptographic operations.