CVE Catalog

CVE-2021-47245

HighCVSS 8.2
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Elevated risk
0.78%

52th percentile - higher than 52% of all known CVEs

Summary

In the Linux kernel, the TCP option parser in synproxy (synproxy_parse_options) could read one byte out of bounds. When the length is 1, the execution flow enters the loop, reads one byte of the opcode, and if the opcode is neither TCPOPT_EOL nor TCPOPT_NOP, it reads one more byte, exceeding the length of 1. The fix adds an early return when length < 0.

Risk Assessment

Out-of-bounds read could lead to information disclosure or system crash, especially in environments with packet filtering.

Recommendation

Apply a Linux kernel update containing the fix that adds a length check and early return in the TCP option parser in synproxy.

Other vulnerabilities in Linux kernel

See all
Original NVD description (English source)

In the Linux kernel, the following vulnerability has been resolved: netfilter: synproxy: Fix out of bounds when parsing TCP options The TCP option parser in synproxy (synproxy_parse_options) could read one byte out of bounds. When the length is 1, the execution flow gets into the loop, reads one byte of the opcode, and if the opcode is neither TCPOPT_EOL nor TCPOPT_NOP, it reads one more byte, which exceeds the length of 1. This fix is inspired by commit 9609dad263f8 ("ipv4: tcp_input: fix stack out of bounds when parsing TCP options."). v2 changes: Added an early return when length < 0 to avoid calling skb_header_pointer with negative length.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS