CVE-2026-68425

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

IB/mad: Drop unmatched RMPP responses before reassembly

Kernel-handled RMPP receive processing starts reassembly for active DATA responses before the response is matched to an outstanding send. The normal match happens later, after ib_process_rmpp_recv_wc() has either assembled a complete message or consumed the segment.

That ordering lets an unsolicited response that routes to a kernel RMPP agent by the high TID bits allocate or extend RMPP receive state before the full TID and source address are checked against a real request. A reordered burst can therefore reach the receive-side insertion path even though the response would not match any send.

For kernel-handled RMPP DATA responses, require the existing ib_find_send_mad() match before entering RMPP reassembly. The matcher already checks the full TID, management class and source address/GID against the agent wait, backlog and in-flight send lists. If there is no match, drop the response without creating RMPP state.

This leaves the RMPP window behavior unchanged and only rejects responses that have no corresponding request.

Weakness

The product does not properly control the allocation and maintenance of a limited resource.

Affected Software

Potential Mitigations

• Mitigation of resource exhaustion attacks requires that the target system either:

• The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.

• The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/147.html
• https://cwe.mitre.org/data/definitions/227.html
• https://cwe.mitre.org/data/definitions/492.html

References

• https://git.kernel.org/stable/c/45416c87ebcece1e90f3bc5bc172d106b77c6b69
• https://git.kernel.org/stable/c/6e1bd7f590b0ccfee07f7fe1d48b92059bd37d72
• https://git.kernel.org/stable/c/9634fb1f4d404f36a20ffbcb8797369db69b06bb
• https://git.kernel.org/stable/c/98d2d468b4faa1fdc68c0c6c238389906ee3490c
• https://git.kernel.org/stable/c/ad9c9ad3204f63a46f0f7de29687a8e512f05e29
• https://git.kernel.org/stable/c/bfb9e8243fd2099d1080d09222964d988f991d9b
• https://git.kernel.org/stable/c/d2e52d610b9b09694261632340b801a421e0b0c5
• https://git.kernel.org/stable/c/dfa535c94406c03d3f0c869ef3ba5528e395737c