CVE-2026-68425 IB/mad: Drop unmatched RMPP responses before reassembly
An attacker can cause a denial of service in the Linux kernel by sending unsolicited InfiniBand RMPP responses that trigger unnecessary state allocation before validation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-68425?
CVE-2026-68425 is a high-severity denial of service vulnerability in Linux, published on 10 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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: CWE-400
Which versions are affected by CVE-2026-68425?
How do I fix CVE-2026-68425?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-68425 being exploited?
There is no known exploitation of CVE-2026-68425 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-68425, DEBIAN-CVE-2026-68425, GHSA-c7q4-7jj2-g2jh, UBUNTU-CVE-2026-68425.