Cisco Email Security Appliance Denial Of Service Vulnerability
Description
A vulnerability in the Transport Layer Security (TLS) protocol implementation of Cisco AsyncOS software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to cause high CPU usage on an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to inefficient processing of incoming TLS traffic. An attacker could exploit this vulnerability by sending a series of crafted TLS packets to an affected device. A successful exploit could allow the attacker to trigger a prolonged state of high CPU utilization. The affected device would still be operative, but response time and overall performance may be degraded.There are no workarounds that address this vulnerability.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
A vulnerability in Cisco AsyncOS TLS implementation allows unauthenticated remote attackers to cause high CPU usage and denial of service on Email Security Appliances.
Vulnerability
The vulnerability resides in the Transport Layer Security (TLS) protocol implementation of Cisco AsyncOS software for Cisco Email Security Appliance (ESA). Affected versions include Cisco ESA software releases 13.5.1-277 and earlier [1]. The issue stems from inefficient processing of incoming TLS traffic, allowing crafted packets to trigger high CPU usage.
Exploitation
An unauthenticated, remote attacker can exploit this vulnerability by sending a series of crafted TLS packets to an affected device [1]. No authentication or special network position is required beyond network reachability. The attacker does not need user interaction.
Impact
Successful exploitation causes a prolonged state of high CPU utilization on the device, leading to degraded response time and overall performance [1]. The device remains operative, but the denial of service condition can disrupt normal email processing.
Mitigation
No workarounds are available for this vulnerability [1]. Cisco has not provided a specific fixed version in the available advisory; customers are advised to monitor the Cisco Security Advisories page for future updates [1].
AI Insight generated on May 25, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.
Affected products
3- Range: N/A
Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
1News mentions
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