CVE-2011-4971 in Memcached
Summary
by MITRE
Multiple integer signedness errors in the (1) process_bin_sasl_auth, (2) process_bin_complete_sasl_auth, (3) process_bin_update, and (4) process_bin_append_prepend functions in Memcached 1.4.5 and earlier allow remote attackers to cause a denial of service (crash) via a large body length value in a packet.
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Analysis
by VulDB Data Team • 01/11/2022
The vulnerability identified as CVE-2011-4971 represents a critical security flaw in Memcached versions 1.4.5 and earlier, specifically affecting the handling of binary protocol packets. This issue stems from multiple integer signedness errors within four distinct functions that process authentication and data manipulation operations. The vulnerability demonstrates a classic example of improper input validation where the software fails to properly validate the size parameters of incoming binary packets, creating opportunities for malicious actors to exploit the system through carefully crafted payloads.
The technical implementation of this vulnerability occurs through four specific functions: process_bin_sasl_auth, process_bin_complete_sasl_auth, process_bin_update, and process_bin_append_prepend. Each of these functions processes binary protocol packets that contain body length values which are not properly validated for signedness constraints. When remote attackers send packets with large body length values that exceed the expected integer limits, the software's handling of these values causes integer overflow conditions that ultimately lead to memory corruption and system crashes. This type of vulnerability falls under the CWE-190 category of Integer Overflow or Wraparound, which is a well-documented weakness in software security that often leads to denial of service conditions and potential privilege escalation.
The operational impact of CVE-2011-4971 is significant as it allows remote attackers to execute denial of service attacks against Memcached servers without requiring authentication or specific privileges. This makes the vulnerability particularly dangerous in production environments where Memcached is used as a caching layer for web applications, database systems, and other critical infrastructure components. The crash conditions can be reliably triggered through network-based attacks, making it possible for adversaries to disrupt services, cause application downtime, and potentially create conditions that could be exploited for more sophisticated attacks. From an attack framework perspective, this vulnerability aligns with ATT&CK technique T1499.004 for Network Denial of Service, where adversaries leverage software flaws to disrupt availability of services.
The root cause of this vulnerability lies in the improper handling of unsigned integer values during packet processing, where signed integer arithmetic operations are performed on data that should be treated as unsigned. This mismatch creates opportunities for attackers to craft packets where the body length field, when interpreted as a signed integer, can cause unexpected behavior in the memory management and allocation routines. The vulnerability is particularly concerning because it affects core authentication and data manipulation functions, meaning that even legitimate users could potentially trigger the denial of service conditions through malformed packets. Organizations running vulnerable versions of Memcached should immediately implement mitigations including updating to patched versions, implementing network-level restrictions, and deploying intrusion detection systems to monitor for exploitation attempts. The vulnerability serves as a reminder of the importance of proper input validation and the potential consequences of integer handling errors in security-critical software components.