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CVE-2026-74626
NTB: ntb_netdev: Preserve RX queue depth on allocation failure
Published 2026-08-22 (2 months ago) by the Linux kernel CNA. Subsystem drivers/net. Debian urgency: not yet assigned.
Debian does not build this code. The per-release build detail is under "Where it lives" below.
What to do, per Debian release
Debian's own status for CVE-2026-74626 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6477-1 · 2026-08-29 · text | 6.12.107-1 | Update the kernel and reboot. DSA-6477-1 shipped the fix on 2026-08-29, in 6.12.107-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
ntb_netdev_rx_handler() hands the received skb to the network stack before allocating its replacement. If the allocation fails, nothing is reposted. Every failure therefore takes one buffer out of the RX queue while the interface remains up, and enough failures eventually stall reception. A retry path could refill the queue later, but ntb_netdev has none. Allocate the replacement first instead. If that fails, drop the packet and repost the same skb. This keeps the queue full and lets packet delivery resume as soon as memory is available again.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/net/ntb_netdev.c
- What this is
- NTB DRIVER COREMAINTAINERS section matched on drivers/net/ntb_netdev.c · ntb@lists.linux.dev · Supported
- Kernel module
- none to look for. The file would have gone into ntb_netdev, and Debian does not compile it into that module, so finding ntb_netdev in lsmod would say nothing about this CVE.
Check it on the machine
grep -w CONFIG_NTB_NETDEV /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian does not build this code. In 5 releases below, every kernel flavour Debian publishes has the switch off, so the vulnerable file is compiled into no kernel binary Debian ships.
- bookworm, trixie, forky, sid, bookworm · linux-6.12n
- n
- not enabled on any flavour - this release does not build the code
- Build switch
- CONFIG_NTB_NETDEV
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-22 (2 months ago)source
- CVSS
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.50%, higher than 41.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/net
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 3.9 | 5.10.267 | 6d7f8a23c130 |
| 3.9 | 5.15.218 | 18781cc0bfb5 |
| 3.9 | 6.1.185 | 272df0fbe6f3 |
| 3.9 | 6.6.154 | fcaf8ba7e56b |
| 3.9 | 6.12.106 | 3f2a15f33f86 |
| 3.9 | 6.18.46 | a4e340971fe8 |
| 3.9 | 7.1.9 | 755fd7843f30 |
| 3.9 | 7.2 | d2121faf133a |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DSA-6477-1 | 2026-08-29 | trixie 6.12.107-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:NAttack vector, network
- The bug is triggered in ntb_netdev_rx_handler() on every Ethernet frame received on the NTB virtual netdev; in dual-controller storage and cluster deployments the NTB interconnect carries bridged or routed IP traffic, so a remote peer can deliver packets that reach this handler without local access to the victim.
- AC:LAttack complexity, low
- An attacker can reliably trigger the failure by flooding the NTB link with packets while inducing GFP_ATOMIC allocation pressure through sustained traffic and/or local memory exhaustion; each failed netdev_alloc_skb permanently consumes one of the 100 RX slots with no recovery path until the interface is restarted.
- PR:NPrivileges required, none
- Reception is driven by raw Ethernet frames from the NTB peer with no authentication, capability checks, or application-layer credentials on the receive path; any host that can send traffic over the established NTB link can reach ntb_netdev_rx_handler().
- UI:NUser interaction, none
- Exploitation requires only that the NTB netdev link already be up in its normal deployment configuration; no victim login, mount, file open, or other interactive action is needed beyond the attacker sending packets over the interconnect.
- S:UScope, unchanged
- The impact is permanent loss of receive capability on the NTB netdev within the same kernel security domain; it does not cross a VM, hypervisor, IOMMU, or other security-authority boundary.
- C:NConfidentiality impact, none
- The defect only leaks RX queue entries on allocation failure and does not involve out-of-bounds access, use-after-free, or any memory read primitive that could disclose kernel data to the attacker.
- I:NIntegrity impact, none
- No kernel or user data is modified; the bug only fails to repost a receive buffer, causing progressive RX queue depletion rather than arbitrary memory writes or code execution.
- A:HAvailability impact, high
- Each allocation failure permanently removes one RX buffer with no refill mechanism, and after NTB_RXQ_SIZE (100) failures reception on the NTB netdev stalls completely while the interface remains up, causing a persistent denial of service on a critical cluster interconnect until manual intervention.