CVE-2026-121603 in Solanum
Summary
by MITRE • 11/03/2026
Solanum before commit 2ea1382 contains a buffer overflow vulnerability in ms_kill() that allows malicious linked servers to corrupt memory by sending an overlong kill reason. Attackers controlling a rogue or compromised peer server can send a reason exceeding KILLLEN that overflows a static 512-byte buffer, crashing the ircd or potentially achieving remote code execution.
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified in Solanum prior to commit 2ea1382 represents a critical memory safety failure within the IRC daemon's process termination logic. Specifically, the flaw resides in the ms_kill() function, which is responsible for handling kill commands initiated by server-to-server communication. In Internet Relay Chat architectures, servers frequently exchange administrative messages to manage network topology and remove malicious or disruptive users. The ms_kill() routine accepts a reason string from linked peer servers to document why a user connection was terminated. However, the implementation fails to validate the length of this incoming reason string against the capacity of the local static buffer allocated for storage. This lack of bounds checking creates a classic stack-based buffer overflow condition that can be triggered remotely by any server connected within the same IRC network topology.
From a technical perspective, the core issue is an improper limit on array indexing or memory copy operations. The code allocates a fixed-size buffer of 512 bytes to hold the kill reason provided by the peer server. When a malicious actor controls a rogue or compromised peer server, they can craft and transmit a kill command containing a reason string that exceeds this 512-byte limit. Because the function does not truncate the input or verify its length before copying it into the static buffer, data from the overflowed portion of the message spills over adjacent memory locations on the stack. This corruption alters critical control flow data such as return addresses, frame pointers, and saved registers. Depending on the specific compiler optimizations, operating system architecture, and available security mitigations like Address Space Layout Randomization or Stack Canaries, this memory corruption can lead to a denial of service via application crash or potentially allow for arbitrary code execution if an attacker can precisely craft the overflow payload to overwrite function pointers with shellcode addresses.
The operational impact of this vulnerability is severe due to its potential for remote exploitation within trusted network boundaries. IRC networks often rely on trust between linked servers, assuming that peer operators will not send malformed administrative commands. An attacker who compromises a single server or operates a rogue node can leverage this flaw to destabilize the entire network infrastructure. A successful exploit results in the immediate crash of the ircd process, causing widespread disconnection for all users associated with that daemon and potentially triggering cascading failures if other servers attempt to reconnect or handle the sudden loss of connectivity. In worst-case scenarios where memory corruption is fully exploitable, an attacker could gain control over the underlying host system running the IRC server, leading to data exfiltration, lateral movement within the network, or use of the compromised machine as a pivot point for further attacks against other internal assets.
This vulnerability aligns with Common Weakness Enumeration CWE-120, which describes buffer copy without checking size limits, and specifically manifests as CWE-121 if it involves stack-based overflow leading to control flow hijacking. In terms of the MITRE ATT&CK framework, this flaw facilitates initial access or privilege escalation through exploitation of a software vulnerability during the execution phase. The attack vector is classified as network-based but requires authentication in the form of valid server linkage credentials, placing it within the context of trusted administrative interfaces being abused. To mitigate this risk, immediate patching to commit 2ea1382 or later versions is required, as these updates introduce proper length validation before memory operations are performed on the kill reason buffer. Additionally, administrators should implement strict input sanitization policies for all server-to-server messages and consider deploying intrusion detection systems capable of identifying anomalous message sizes in IRC protocol traffic to provide an additional layer of defense against exploitation attempts while patches are being deployed across the network infrastructure.