CVE-2020-24339 in picoTCP
Summary
by MITRE • 12/12/2020
An issue was discovered in picoTCP and picoTCP-NG through 1.7.0. The DNS domain name record decompression functionality in pico_dns_decompress_name() in pico_dns_common.c does not validate the compression pointer offset values with respect to the actual data present in a DNS response packet, causing out-of-bounds reads that lead to Denial-of-Service.
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Analysis
by VulDB Data Team • 12/16/2020
The vulnerability identified as CVE-2020-24339 affects picoTCP and picoTCP-NG versions through 1.7.0, specifically within the DNS domain name record decompression functionality. This issue resides in the pico_dns_decompress_name() function located in pico_dns_common.c, where the implementation fails to properly validate compression pointer offset values against the actual data present in DNS response packets. The root cause stems from inadequate bounds checking during the decompression process, creating a scenario where maliciously crafted DNS responses can trigger memory access violations.
The technical flaw manifests as out-of-bounds read operations that occur when the DNS decompression function processes compression pointers without verifying that the referenced offset values fall within the legitimate bounds of the received DNS packet data. This type of vulnerability falls under CWE-129, which specifically addresses insufficient input validation, and more broadly relates to CWE-787, representing out-of-bounds write operations that can lead to system instability. The function processes DNS compression pointers without ensuring that the pointer values reference valid memory locations within the packet buffer, allowing attackers to craft specially formatted DNS responses that cause the application to read beyond allocated memory boundaries.
From an operational impact perspective, this vulnerability creates a reliable denial-of-service condition that can be exploited by remote attackers without requiring authentication or specialized privileges. When a vulnerable picoTCP or picoTCP-NG implementation receives a malicious DNS response containing crafted compression pointers, the system will attempt to read memory locations beyond the legitimate packet boundaries, resulting in application crashes or system instability. The vulnerability affects any system utilizing these TCP/IP stack implementations in DNS client or server configurations, potentially disrupting network services and creating availability issues for affected systems. This aligns with ATT&CK technique T1499.004, which covers network denial of service attacks that target application availability.
The mitigation strategies for this vulnerability primarily involve upgrading to patched versions of picoTCP or picoTCP-NG beyond the affected 1.7.0 release, where the decompression function has been enhanced to properly validate compression pointer offsets against the actual packet data boundaries. Additionally, network administrators should implement DNS filtering mechanisms that can detect and block malformed DNS responses containing suspicious compression pointer patterns. Organizations utilizing these TCP/IP stacks in embedded systems or network appliances should conduct thorough testing of patched implementations to ensure that the remediation does not introduce compatibility issues with existing network configurations. The fix should include comprehensive bounds checking that validates all compression pointer values against the packet buffer limits before any memory access operations are performed, thereby preventing the out-of-bounds read conditions that lead to system instability.