Riskcovery

CVE-2021-47593

mptcp: clear 'kern' flag from fallback sockets

State
Published
Severity
Not scored
Published
Jun 19, 2024
Updated
May 11, 2026
Reserved
May 24, 2024

Read the record on cve.org

Description

In the Linux kernel, the following vulnerability has been resolved:

mptcp: clear 'kern' flag from fallback sockets

The mptcp ULP extension relies on sk->sk_sock_kern being set correctly: It prevents setsockopt(fd, IPPROTO_TCP, TCP_ULP, "mptcp", 6); from working for plain tcp sockets (any userspace-exposed socket).

But in case of fallback, accept() can return a plain tcp sk. In such case, sk is still tagged as 'kernel' and setsockopt will work.

This will crash the kernel, The subflow extension has a NULL ctx->conn mptcp socket:

BUG: KASAN: null-ptr-deref in subflow_data_ready+0x181/0x2b0 Call Trace: tcp_data_ready+0xf8/0x370 [..]

Scores

The record has no CVSS score.

Weaknesses

The record names no weakness.

Affected Products

ProductVersions
LinuxLinux
  • cf7da0d66cc1a2a19fc5930bb746ffbb2d4cd1be to before 451f1eded7f56e93aaf52eb547ba97742d9c0e97Affected
  • cf7da0d66cc1a2a19fc5930bb746ffbb2d4cd1be to before c26ac0ea3a91c210cf90452e625dc441adf3e549Affected
  • cf7da0d66cc1a2a19fc5930bb746ffbb2d4cd1be to before d6692b3b97bdc165d150f4c1505751a323a80717Affected
LinuxLinux
  • 5.6Affected
  • before 5.6Not affected
  • 5.10.88 through 5.10.*Not affected
  • 5.15.11 through 5.15.*Not affected
  • 5.16 and laterNot affected

References

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