CVE-2026-98449 smb: client: delete compound mids on send failure before unlock
A double credit release in the Linux kernel SMB client can cause a kernel warning and potential denial of service when a compound request send fails.
- 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-2026-98449?
CVE-2026-98449 is a denial of service vulnerability in Linux, published on 18 Oct 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:
smb: client: delete compound mids on send failure before unlock
When sending a compound request fails, smb_send_rqst() kicks off a reconnect. compound_send_recv() still has those mids on pending_mid_q, but it unlocks the server without removing them first.
During reconnect, cifs_abort_connection() walks pending_mid_q and runs each mid callback. With no response yet, those callbacks return credits and drop in_flight. Then compound_send_recv()'s send-error path returns the same credits again. in_flight ends up decremented twice and smb2_add_credits() WARNs.
syzbot hits this during SMB2_negotiate when the socket send fails.
cifs_call_async() already calls delete_mid() before unlock on send failure. Do the same for compound chains and set cancelled_mid[] so the out: path does not delete them again.
Which versions are affected by CVE-2026-98449?
How do I fix CVE-2026-98449?
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-2026-98449 being exploited?
There is no known exploitation of CVE-2026-98449 in the wild and no public exploit code.
Sources
Also known as AZL-109380, BELL-CVE-2026-98449, DEBIAN-CVE-2026-98449, GHSA-2758-q84j-4rxj, UBUNTU-CVE-2026-98449.