CVE-2026-93561 in Apache Camel for Spring Boot
Summary
by MITRE • 09/18/2026
Memcache binary codec signed/unsigned type mismatch causes frame desynchronization and response smuggling
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Analysis
by VulDB Data Team • 09/18/2026
The vulnerability identified in the Memcached binary protocol implementation stems from a critical type mismatch between signed and unsigned integer handling during the parsing of incoming network frames. In systems utilizing the binary interface, data is transmitted as structured packets containing headers that dictate payload length, command codes, and other metadata fields. These header fields are typically defined as 32-bit integers within the Memcached protocol specification. However, when a client library or server implementation incorrectly interprets these unsigned integer values as signed integers during deserialization, it introduces a fundamental logical error in how packet boundaries are calculated. This discrepancy becomes particularly acute when high-order bits are set in length fields that would normally represent large positive numbers but are instead interpreted as negative values due to two's complement representation rules inherent in signed arithmetic operations.
This misinterpretation leads directly to frame desynchronization, where the parser loses track of the current packet boundary within the TCP stream or UDP datagram sequence. Instead of correctly advancing the read pointer by the actual payload size indicated by the unsigned value, the system may attempt to skip a negative number of bytes or fail to advance at all if it treats the length as invalid due to sign extension errors. Consequently, subsequent data intended for one request is misaligned and potentially consumed as part of another command's header or payload. This structural corruption of the communication stream creates an environment where an attacker can manipulate the sequence of operations processed by the server without necessarily breaking the connection immediately, allowing for stealthier exploitation attempts that evade standard intrusion detection signatures focused on malformed packet rejection.
The operational impact of this desynchronization is severe and facilitates response smuggling attacks. By carefully crafting requests with specific length fields that exploit the signed-unsigned mismatch, an attacker can inject commands into a legitimate session or cause the server to process out-of-order instructions. For instance, if a request for data retrieval is followed by a malicious write operation in the same stream, frame desynchronization might allow the write command to be interpreted as part of the response body for the previous read, or vice versa. This can lead to unauthorized modification of cached data, denial of service through resource exhaustion caused by processing unexpected commands, or information disclosure if sensitive keys are inadvertently returned due to misaligned parsing logic. The ability to smuggle responses also means that an attacker could potentially manipulate cache consistency, leading to application-level vulnerabilities such as cache poisoning where stale or malicious content is served to legitimate users based on the corrupted state of the server's internal buffers.
From a standards perspective, this vulnerability aligns with CWE-190 Integer Overflow Wraparound and CWE-682 Incorrect Calculation, specifically regarding type conversion errors that lead to logic flaws in boundary checks. The exploitation technique mirrors aspects of ATT&CK tactic T1557 Adversary-in-the-Middle, as the attacker intercepts or manipulates the flow of data between client and server by exploiting protocol state confusion. Furthermore, it relates to CWE-20 Improper Input Validation because the system fails to correctly validate the semantic meaning of input fields based on their defined types within the protocol specification. The failure lies not in rejecting invalid characters but in misinterpreting valid binary representations due to incorrect type casting during internal processing.
Mitigation strategies must focus on rigorous enforcement of data typing throughout the parsing pipeline. Developers should ensure that all integer fields extracted from network packets are explicitly cast and validated against their expected unsigned ranges before being used for memory allocation or stream positioning logic. Implementing strict length validation checks that reject any value exceeding maximum allowable payload sizes can prevent buffer overflows associated with large negative interpretations of signed integers. Additionally, adopting a state machine approach to protocol parsing that resets its state upon detecting desynchronization errors can limit the window of opportunity for response smuggling attacks. Upgrading to patched versions of Memcached client libraries and server implementations is essential, as these updates typically include corrected type handling routines that properly distinguish between signed and unsigned contexts during binary codec operations. Network-level monitoring should also be enhanced to detect anomalous patterns in packet sizes and sequence numbers that may indicate active exploitation attempts leveraging this desynchronization flaw.