A vulnerability in the mux_h2.c source code file of HAProxy could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on a targeted system.
The vulnerability is due to improper H2 frame length checking by the affected software. The H2 frame length is checked against the max_frame_size setting instead of being checked against the bufsize. An attacker could exploit this vulnerability by sending a request that submits a large H2 frame to the targeted system. An exploit could cause the affected software on the system to crash, resulting in a DoS condition.
HAProxy has confirmed the vulnerability and released software updates.
To exploit this vulnerability, an attacker must send a crafted request that submits a large H2 frame to the targeted system, which may require the attacker to have access to the same trusted, internal network as the system. This access requirement may reduce the likelihood of a successful exploit. In addition, the large H2 frame must be advertised in the SETTINGS frame to exploit this vulnerability.
Administrators are advised to apply the appropriate updates.
Administrators are advised to allow only trusted users to have network access.
Administrators are advised to run both firewall and antivirus applications to minimize the potential of inbound and outbound threats.
Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
Administrators can help protect affected systems from external attacks by using a solid firewall strategy.
Administrators are advised to monitor affected systems.
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Cisco Multivendor Vulnerability Alerts respond to vulnerabilities identified in third-party vendors' products. These alerts contain information compiled from diverse sources and provide comprehensive technical descriptions, objective analytical assessments, workarounds and practical safeguards, and links to vendor advisories and patches.