CVE-2025-68227: mptcp: Fix proto fallback detection with BPF
In the Linux kernel, the following vulnerability has been resolved:
mptcp: Fix proto fallback detection with BPF
The sockmap feature allows bpf syscall from userspace, or based on bpf sockops, replacing the skprot of sockets during protocol stack processing with sockmap's custom read/write interfaces. ''' tcprcvstateprocess() synrecvsock()/subflowsynrecvsock() tcpinittransfer(BPFSOCKOPSPASSIVEESTABLISHEDCB) bpfskopsestablished <== sockops bpfsockmapupdate(sk) <== call bpf helper tcpbpfupdateproto() <== update skprot '''
When the server has MPTCP enabled but the client sends a TCP SYN without MPTCP, subflowsynrecvsock() performs a fallback on the subflow, replacing the subflow sk's skprot with the native skprot. ''' subflowsynrecvsock() subflowulpfallback() subflowdropctx() mptcpsubflowopsundooverride() '''
Then, this subflow can be normally used by sockmap, which replaces the native skprot with sockmap's custom skprot. The issue occurs when the user executes accept::mptcpstreamaccept::mptcpfallbacktcpops(). Here, it uses sk->skprot to compare with the native skprot, but this is incorrect when sockmap is used, as we may incorrectly set sk->sksocket->ops.
This fix uses the more generic skfamily for the comparison instead.
Additionally, this also prevents a WARNING from occurring:
result from ./scripts/decodestacktrace.sh: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 337 at net/mptcp/protocol.c:68 mptcpstreamaccept \ (net/mptcp/protocol.c:4005) Modules linked in: ...
PKRU: 55555554 Call Trace: <TASK> doaccept (net/socket.c:1989) sysaccept4 (net/socket.c:2028 net/socket.c:2057) x64sysaccept (net/socket.c:2067) x64syscall (arch/x86/entry/syscall64.c:41) dosyscall64 (arch/x86/entry/syscall64.c:63 arch/x86/entry/syscall64.c:94) entrySYSCALL64afterhwframe (arch/x86/entry/entry64.S:130) RIP: 0033:0x7f87ac92b83d
---[ end trace 0000000000000000 ]---
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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Event History
Frequently Asked Questions
What is the severity of CVE-2025-68227?
CVE-2025-68227 has a moderate severity rating due to the potential for unintended protocol behavior in MPTCP.
How do I fix CVE-2025-68227?
To fix CVE-2025-68227, you should upgrade your Linux kernel to the latest patched version as provided by your distribution.
Which versions of the Linux kernel are affected by CVE-2025-68227?
Specific affected versions of the Linux kernel have not been detailed, but it is advisable to check with your distribution for any kernel vulnerabilities.
What components are impacted by CVE-2025-68227?
CVE-2025-68227 specifically impacts the sockmap feature and its interaction with the MPTCP protocol in the Linux kernel.
Is CVE-2025-68227 actively being exploited?
As of the last updates, there is no public information indicating that CVE-2025-68227 is currently being exploited in the wild.