CVE-2010-2836 in IOS
Summary
by MITRE
Memory leak in the SSL VPN feature in Cisco IOS 12.4, 15.0, and 15.1, when HTTP port redirection is enabled, allows remote attackers to cause a denial of service (memory consumption) by improperly disconnecting SSL sessions, leading to connections that remain in the CLOSE-WAIT state, aka Bug ID CSCtg21685.
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Analysis
by VulDB Data Team • 09/25/2021
The vulnerability described in CVE-2010-2836 represents a critical memory management flaw within Cisco IOS operating systems affecting versions 12.4, 15.0, and 15.1. This issue specifically targets the SSL VPN functionality when HTTP port redirection is enabled, creating a condition where improperly terminated SSL sessions fail to release allocated memory resources. The flaw manifests through connections remaining in the CLOSE-WAIT state indefinitely, which constitutes a denial of service condition that progressively consumes available system memory. This vulnerability falls under the CWE-404 category of Improper Resource Release or Unmanagement, specifically addressing memory leak conditions that occur during network protocol handling. The technical implementation involves the SSL VPN module's failure to properly clean up session state information when SSL connections are terminated without following standard protocol closure sequences, particularly when HTTP port redirection is active. This misconfiguration creates a resource exhaustion scenario where the system's memory consumption increases continuously until system stability is compromised.
The operational impact of this vulnerability extends beyond simple memory consumption to affect overall network infrastructure reliability and availability. When multiple attackers exploit this condition, the cumulative effect can lead to complete system unresponsiveness, requiring manual intervention through device rebooting to restore normal operations. The vulnerability's remote exploitability means that attackers do not require physical access or local network privileges to initiate the memory leak condition, making it particularly dangerous for publicly accessible SSL VPN endpoints. Network administrators face significant challenges in detecting this issue since the memory consumption occurs gradually and may not immediately trigger system alerts. The CLOSE-WAIT state persistence indicates that the TCP connection management protocol is not properly handling the termination sequence, which violates standard network communication protocols and creates a persistent resource drain that can affect other network services running on the same device.
Mitigation strategies for CVE-2010-2836 should focus on immediate patch application through Cisco's security advisories, specifically addressing the memory management issues within the SSL VPN implementation. Network administrators should implement monitoring solutions that track memory consumption patterns and connection states to detect early signs of the vulnerability exploitation. The recommended approach includes disabling HTTP port redirection when SSL VPN services are active, as this configuration element directly contributes to the memory leak condition. Organizations should also consider implementing connection rate limiting and session timeout mechanisms to minimize the impact of potential exploitation attempts. From an operational security perspective, the vulnerability aligns with ATT&CK technique T1499.004 for network denial of service attacks, where adversaries leverage memory exhaustion to disrupt service availability. Additionally, this vulnerability demonstrates characteristics of T1566.001 for credential harvesting through network services, as compromised systems may become unusable for legitimate VPN access. The fix implementation requires careful consideration of network topology and service dependencies, as disabling certain SSL VPN features may impact legitimate user access. Regular security assessments should verify that patches have been properly applied and that no residual memory leak conditions persist, particularly in environments where legacy systems continue to operate with minimal maintenance windows.