CVE-2023-34100 in Contiki-NG
Summary
by MITRE • 06/09/2023
Contiki-NG is an open-source, cross-platform operating system for IoT devices. When reading the TCP MSS option value from an incoming packet, the Contiki-NG OS does not verify that certain buffer indices to read from are within the bounds of the IPv6 packet buffer, uip_buf. In particular, there is a 2-byte buffer read in the module os/net/ipv6/uip6.c. The buffer is indexed using 'UIP_IPTCPH_LEN + 2 + c' and 'UIP_IPTCPH_LEN + 3 + c', but the uip_buf buffer may not have enough data, resulting in a 2-byte read out of bounds. The problem has been patched in the "develop" branch of Contiki-NG, and is expected to be included in release 4.9. Users are advised to watch for the 4.9 release and to upgrade when it becomes available. There are no workarounds for this vulnerability aside from manually patching with the diff in commit `cde4e9839`.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 07/07/2023
The vulnerability CVE-2023-34100 affects Contiki-NG, a widely-used open-source operating system designed for Internet of Things deployments. This embedded operating system provides essential networking capabilities for resource-constrained devices, making it a critical component in numerous IoT infrastructure implementations. The flaw resides within the TCP MSS (Maximum Segment Size) option processing functionality, specifically in how the system handles incoming IPv6 packets containing TCP options. The vulnerability demonstrates a classic buffer over-read condition that could potentially compromise the integrity and stability of IoT devices running this operating system.
The technical implementation of this vulnerability occurs in the os/net/ipv6/uip6.c module where the Contiki-NG stack processes TCP header options. When parsing TCP MSS options from incoming packets, the system performs direct buffer indexing operations using expressions 'UIP_IPTCPH_LEN + 2 + c' and 'UIP_IPTCPH_LEN + 3 + c' without first validating that these indices remain within the bounds of the uip_buf buffer. This buffer over-read scenario specifically affects a 2-byte read operation that accesses memory locations beyond the allocated packet buffer space. The vulnerability is classified under CWE-129 as an "Improper Validation of Array Index" and represents a direct violation of memory safety principles. The issue stems from the lack of bounds checking before buffer access, a common pattern in embedded systems where performance considerations sometimes override defensive programming practices.
The operational impact of CVE-2023-34100 extends beyond simple memory corruption, as it could enable remote attackers to potentially manipulate device behavior or extract sensitive information from memory locations. In IoT environments where Contiki-NG devices often handle critical infrastructure functions, such a vulnerability could lead to device instability, denial of service conditions, or even facilitate more sophisticated attacks. The vulnerability affects devices that process TCP packets with MSS options, which is common in normal network operations, making exploitation relatively straightforward. From an ATT&CK framework perspective, this vulnerability could enable techniques such as information gathering through memory disclosure and privilege escalation by corrupting system memory, particularly in environments where compromised devices might be used as part of larger attack chains. The lack of workarounds means that affected systems remain vulnerable until proper patching occurs, creating potential exposure windows.
The remediation approach for CVE-2023-34100 involves upgrading to Contiki-NG release 4.9 or applying the specific patch referenced in commit cde4e9839. This patch addresses the fundamental bounds checking issue by ensuring that buffer indices are validated before access operations occur. Organizations deploying Contiki-NG systems should monitor the official release channels for version 4.9 and implement upgrades as soon as possible to mitigate the risk. Security teams should also consider implementing network monitoring to detect anomalous TCP packet patterns that might indicate exploitation attempts, particularly focusing on malformed MSS options that could trigger the vulnerable code path. The vulnerability highlights the importance of defensive programming practices in embedded systems where resource constraints and performance requirements can sometimes lead to security oversights, particularly in protocols that handle variable-length options in network packets.