CVE-2022-24903 in Communications Diameter Signaling Router
Summary
by MITRE • 05/06/2022
Rsyslog is a rocket-fast system for log processing. Modules for TCP syslog reception have a potential heap buffer overflow when octet-counted framing is used. This can result in a segfault or some other malfunction. As of our understanding, this vulnerability can not be used for remote code execution. But there may still be a slight chance for experts to do that. The bug occurs when the octet count is read. While there is a check for the maximum number of octets, digits are written to a heap buffer even when the octet count is over the maximum, This can be used to overrun the memory buffer. However, once the sequence of digits stop, no additional characters can be added to the buffer. In our opinion, this makes remote exploits impossible or at least highly complex. Octet-counted framing is one of two potential framing modes. It is relatively uncommon, but enabled by default on receivers. Modules `imtcp`, `imptcp`, `imgssapi`, and `imhttp` are used for regular syslog message reception. It is best practice not to directly expose them to the public. When this practice is followed, the risk is considerably lower. Module `imdiag` is a diagnostics module primarily intended for testbench runs. We do not expect it to be present on any production installation. Octet-counted framing is not very common. Usually, it needs to be specifically enabled at senders. If users do not need it, they can turn it off for the most important modules. This will mitigate the vulnerability.
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Analysis
by VulDB Data Team • 05/05/2026
The CVE-2022-24903 vulnerability affects rsyslog's TCP syslog reception modules, specifically targeting heap buffer overflow conditions during octet-counted framing processing. This vulnerability resides within the core log processing functionality of rsyslog, a widely deployed system for log aggregation and management across enterprise environments. The flaw manifests when the system processes TCP syslog messages using octet-counted framing, a protocol mechanism that prepends message length information to syslog data streams. The vulnerability is classified under CWE-121 as a heap-based buffer overflow, representing a critical memory safety issue that can compromise system stability and potentially lead to denial of service conditions.
The technical implementation of this vulnerability occurs during the parsing of octet count values within the TCP reception modules. While the system implements validation checks for maximum octet counts, the design flaw allows digits to be written to heap buffers even when the octet count exceeds defined limits. This creates a scenario where buffer boundaries are exceeded during the digit processing phase, potentially causing segmentation faults or system malfunctions. The vulnerability affects multiple core modules including imtcp, imptcp, imgssapi, and imhttp, which are responsible for receiving and processing syslog messages over TCP connections. The buffer overflow condition specifically occurs when the system reads octet count values and subsequently writes digit characters to memory locations without proper boundary enforcement, creating a potential for memory corruption that aligns with ATT&CK technique T1499.201 for network denial of service.
The operational impact of this vulnerability extends beyond simple system instability, as it represents a potential vector for service disruption and system compromise. While current analysis indicates that remote code execution is not readily achievable due to the limited nature of the overflow and the specific conditions required for exploitation, the vulnerability still presents significant security risks. The flaw can be leveraged to cause system crashes, leading to denial of service conditions that can impact log aggregation services critical to security monitoring and incident response operations. The vulnerability's potential for exploitation aligns with ATT&CK tactic TA0040 (defense evasion) and TA0006 (credential access) through system instability and potential privilege escalation pathways. Organizations relying on rsyslog for log collection and processing face increased risk of operational disruptions, particularly in environments where continuous log availability is essential for security operations.
Mitigation strategies for CVE-2022-24903 focus on both configuration changes and operational best practices to reduce exposure risk. The most effective immediate mitigation involves disabling octet-counted framing when it is not specifically required, particularly in production environments where the feature is not essential. System administrators should review their rsyslog configurations and disable the octet-counted framing option for TCP reception modules unless there is a specific business requirement. The recommended approach aligns with security best practices for network service hardening and follows the principle of least privilege by minimizing attack surface. Additionally, organizations should ensure that TCP syslog reception modules are not directly exposed to untrusted networks, as this practice significantly reduces the likelihood of exploitation. The vulnerability affects modules such as imtcp, imptcp, imgssapi, and imhttp which are typically deployed in internal network segments rather than public-facing services. Security teams should implement network segmentation controls to isolate these modules and prevent direct exposure to external threats. The imdiag module, while potentially affected, is primarily intended for testing and diagnostic purposes, making it unlikely to be present in production environments and thus reducing overall risk exposure.
The broader implications of this vulnerability highlight the importance of memory safety in network services and log processing systems. This flaw demonstrates how seemingly simple protocol parsing logic can introduce critical security risks when proper input validation and buffer boundary checking are not implemented. The vulnerability serves as a reminder of the need for comprehensive security testing of network services, particularly those handling untrusted input data streams. Organizations should conduct regular security assessments of their log processing infrastructure and ensure that all network services are updated with the latest security patches. The vulnerability also emphasizes the importance of monitoring and logging systems for anomalous behavior that might indicate exploitation attempts. Given that octet-counted framing is enabled by default on receivers, system administrators must proactively review their configurations and implement security controls to prevent potential exploitation. The risk assessment should consider both the technical complexity required for exploitation and the potential impact on system availability and security monitoring capabilities. Regular security updates and vulnerability management processes should include specific attention to log processing systems and their underlying protocols to prevent similar vulnerabilities from being exploited in the future.