CVE-2026-93228 svcrdma: Reject Write/Reply chunks with segcount 0
A remote peer can cause a denial of service in the Linux kernel by sending malformed RDMA chunks with zero segments, bypassing validation checks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-93228?
CVE-2026-93228 is a critical denial of service vulnerability in Linux, published on 24 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
svcrdma: Reject Write/Reply chunks with segcount 0
A peer can send a Write or Reply chunk whose segcount field is zero. xdr_check_write_chunk() only rejects segcount > rc_maxpages, so zero passes the range check, and xdr_inline_decode(stream, 0) returns the current (non-NULL) cursor without advancing. The function returns true and pcl_alloc_write() then links a struct svc_rdma_chunk with ch_segcount == 0 onto rc_write_pcl or rc_reply_pcl.
An earlier patch in this series made pcl_for_each_segment() safe for ch_segcount == 0, so this no longer drives the memory walk it used to. Rejecting the malformed frame at the decode boundary is still worthwhile as defense in depth: it keeps degenerate zero-segment chunks off the parsed chunk lists entirely, so any future consumer that walks ch_segments directly cannot observe one, and it makes the zero-floor easy to backport to trees where the macro change is more intrusive. RFC 8166 has no meaning for a Write/Reply chunk that describes no remote buffer, so no legitimate client is affected.
xdr_check_reply_chunk() funnels Reply chunks through xdr_check_write_chunk() and inherits the same rejection.
pcl_alloc_write() also links each chunk onto the parsed chunk list before filling its segment array. If a future change weakens the segcount-0 rejection, an incomplete chunk is visible to consumers during the fill loop. Reorder so that list_add_tail() follows the segment fill loop, ensuring only fully-populated chunks appear on the list.
Which versions are affected by CVE-2026-93228?
How do I fix CVE-2026-93228?
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-2026-93228 being exploited?
There is no known exploitation of CVE-2026-93228 in the wild and no public exploit code.
Sources
Also known as AZL-103850, BELL-CVE-2026-93228, DEBIAN-CVE-2026-93228, GHSA-g29j-c673-5ccw, UBUNTU-CVE-2026-93228.