CVE-2021-27697: 
NixOS vulnerability analysis and mitigation

RIOT-OS 2021.01 contains a buffer overflow vulnerability in sys/net/gnrc/routing/rpl/gnrc_rpl_validation.c through the gnrc_rpl_validation_options() function. The vulnerability was discovered and disclosed in February 2021 (CISA Bulletin).

The vulnerability exists in the gnrc_rpl_validation_options function where it casts packed structs without performing prior bounds checks. For example, in the handler for GNRC_RPL_OPT_PAD1, the code is missing checks like 'if (len < sizeof(gnrc_rpl_opt_t)) return false;'. This can lead to out-of-bounds reads when accessing opt->length or opt->type on subsequent iterations (GitHub Issue). The vulnerability has been assigned a CVSS score of 7.5, indicating high severity (CISA Bulletin).

The buffer overflow vulnerability can result in heap-buffer-overflow conditions, potentially leading to application crashes and arbitrary code execution. When exploited, the vulnerability allows reading memory beyond allocated buffer boundaries (GitHub Issue).

The vulnerability can be triggered by sending specially crafted network packets to the affected system. A proof-of-concept exploit has been demonstrated using a malformed packet that causes the application to crash with a heap-buffer-overflow error (GitHub Issue).