CVE-2026-44236: 
Wolfi vulnerability analysis and mitigation

CVE-2026-44236 is a heap buffer overflow vulnerability in the rabbitmq-c (librabbitmq) C client library, triggered during the AMQP login handshake when a malicious or on-path server sends a connection.tune frame with an undersized frame_max value. It affects rabbitmq-c versions ≤0.15.0, with the fix introduced in version 0.16.0. The vulnerability was published on June 9, 2026, and was discovered through Anthropic's LLM-assisted vulnerability research, subsequently validated by Trail of Bits. It carries a CVSS v3.1 score of 7.1 (High) (GitHub Advisory, Ubuntu Advisory).

The root cause is a missing minimum size check in amqp_tune_connection() (CWE-122: Heap-based Buffer Overflow). In librabbitmq/amqp_socket.c, the amqp_login_inner() function unconditionally accepts a server-provided frame_max value smaller than the client's requested value, then passes it to amqp_tune_connection(), which uses it directly as the outbound buffer size via realloc(). If the server sends frame_max = 1, the buffer is resized to 1 byte; the subsequent serialization of the connection.tune-ok response writes a 2-byte value at offset 1, overflowing the heap allocation. The AMQP specification documents a minimum frame size of 4096 bytes (AMQP_FRAME_MIN_SIZE), but this constraint is not enforced. A public PoC using ASAN and the existing fuzz_server harness is included in the advisory (GitHub Advisory).

Successful exploitation causes client-side heap memory corruption, with the most realistic outcome being a denial of service (process crash or abort) in any application using rabbitmq-c to connect to AMQP servers. Arbitrary code execution is theoretically possible depending on allocator behavior and heap layout, but has not been demonstrated. The vulnerability is exploitable before authentication completes, meaning no credentials are required from the attacker's side, and it affects all client applications linking against librabbitmq ≤0.15.0 (GitHub Advisory, Ubuntu Advisory).

A public proof-of-concept is available in the GitHub Security Advisory, including a binary payload and build instructions using ASAN. The vulnerability is remotely triggerable by a malicious AMQP server before authentication, or by an on-path attacker against plaintext AMQP traffic; user interaction is required in the sense that the victim client must initiate a connection. No in-the-wild exploitation has been reported, and the CVE is not currently listed in the CISA KEV catalog. The vulnerability was detected by Nessus (plugin 320345) and Qualys (plugin 6280220) scanners (GitHub Advisory, Feedly).

1. Set up a malicious AMQP server: Deploy a server (or perform an on-path interception) that responds to AMQP client connections with a crafted connection.tune frame containing frame_max = 1 (or any value below 4096).
2. Wait for victim client to connect: Any application using rabbitmq-c ≤0.15.0 that calls amqp_login() against the attacker-controlled server will trigger the vulnerable code path.
3. Deliver the malicious frame: Send the crafted binary payload — as demonstrated in the PoC — which includes a connection.start frame followed by a connection.tune frame with frame_max = 0x00000001.
4. Trigger heap buffer overflow: The client's amqp_tune_connection() reallocates the outbound buffer to 1 byte; the subsequent amqp_send_method_inner() call writes the connection.tune-ok frame header, overflowing the heap allocation.
5. Achieve denial of service or code execution: Under hardened allocators or ASAN, the process aborts immediately. In production environments without such protections, heap layout-dependent code execution may be possible (GitHub Advisory).

• Network: Unexpected AMQP connection.tune frames from a server with frame_max values below 4096 (0x1000); plaintext AMQP traffic (port 5672) with anomalous frame headers.
• Process: Sudden crash or abort of applications using librabbitmq during the login/handshake phase; ASAN or heap sanitizer reports referencing amqp_tune_connection(), amqp_frame_to_bytes(), or amqp_login_inner().
• Logs: Application logs showing connection failures or segmentation faults immediately after connecting to an AMQP broker; core dumps from processes linking librabbitmq with stack traces involving amqp_e16, amqp_frame_to_bytes, or amqp_send_method_inner (GitHub Advisory).

Upgrade rabbitmq-c to version 0.16.0, which enforces a minimum frame_max value of AMQP_FRAME_MIN_SIZE (4096 bytes) before resizing the outbound buffer. Ubuntu has released patched packages: librabbitmq4 0.15.0-1ubuntu0.26.04.1 (Ubuntu 26.04), 0.15.0-1ubuntu0.25.10.1 (Ubuntu 25.10), 0.11.0-1ubuntu0.1 (Ubuntu 24.04 LTS), and 0.10.0-1ubuntu2.1 (Ubuntu 22.04 LTS). As a workaround where patching is not immediately possible, restrict client connections to trusted, authenticated AMQP brokers and use TLS to prevent on-path attacks (GitHub Advisory, Ubuntu Advisory).

The vulnerability was discovered as part of Anthropic's research into using large language models for automated vulnerability discovery in open source software; Trail of Bits independently triaged and validated the findings before disclosure. The advisory was published by the rabbitmq-c maintainer (alanxz) on June 9, 2026, with credit to researcher kevin-valerio. Social media activity was noted via a ThreatCluster post on June 16, 2026 (GitHub Advisory).