CVE-2020-17440 in uIP
Summary
by MITRE • 12/12/2020
An issue was discovered in uIP 1.0, as used in Contiki 3.0 and other products. The code that parses incoming DNS packets does not validate that domain names present in the DNS responses have '\0' termination. This results in errors when calculating the offset of the pointer that jumps over domain name bytes in DNS response packets when a name lacks this termination, and eventually leads to dereferencing the pointer at an invalid/arbitrary address, within newdata() and parse_name() in resolv.c.
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Analysis
by VulDB Data Team • 12/16/2020
The vulnerability identified as CVE-2020-17440 represents a critical buffer over-read condition within the uIP 1.0 networking stack implementation used in Contiki 3.0 and related systems. This flaw exists in the DNS packet parsing functionality where the code fails to properly validate domain name termination within DNS responses. The issue stems from insufficient input validation mechanisms that allow malformed DNS packets to bypass standard parsing checks, creating a scenario where domain names may lack the expected null termination character that is fundamental to proper string handling in C-based applications. This specific weakness manifests in the resolv.c file within the newdata() and parse_name() functions where pointer arithmetic operations occur without adequate bounds checking.
The technical exploitation of this vulnerability occurs when a malicious DNS server responds with a packet containing a domain name that is not properly null-terminated. During packet parsing, the code attempts to calculate offsets for pointer jumps that traverse domain name bytes, but without proper termination validation, these calculations become invalid. This leads to arbitrary pointer dereferencing at unpredictable memory addresses, creating potential for denial of service conditions or more severe exploitation scenarios. The vulnerability directly maps to CWE-129, which describes improper validation of array index or pointer offset, and CWE-121, which covers stack-based buffer overflow conditions. The flaw demonstrates characteristics consistent with the ATT&CK technique T1059.007 for DNS tunneling and command and control communications, as malicious actors could potentially leverage this to manipulate network communications.
The operational impact of CVE-2020-17440 extends beyond simple service disruption to potentially enable remote code execution in vulnerable systems. When exploited, the arbitrary pointer dereference can cause system crashes, memory corruption, or in more sophisticated attack scenarios, provide attackers with opportunities to execute malicious code within the context of the affected application. Systems running Contiki 3.0 or other products utilizing the vulnerable uIP 1.0 implementation are particularly at risk, as these platforms often operate in embedded environments where memory management is constrained and recovery mechanisms may be limited. The vulnerability affects network infrastructure devices, IoT systems, and embedded applications that rely on DNS resolution for network operations, making it a significant concern for industrial control systems and network security deployments. Organizations should implement immediate mitigations including firmware updates, network segmentation, DNS filtering mechanisms, and monitoring for suspicious DNS traffic patterns that could indicate exploitation attempts.