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CVE-2026-80987
NTB: ntb_transport: Reject oversized TX buffers
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem drivers/ntb. 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-2026-80987 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-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
ntb_process_tx() handles an oversized buffer by calling tx_handler() with a NULL data pointer and returning success. ntb_netdev therefore neither frees the skb in its completion callback nor takes its enqueue error path, leaking it. Reject oversized buffers in ntb_transport_tx_enqueue() before acquiring a queue entry and return -EMSGSIZE. The caller retains ownership of the buffer, and the preceding netdev patch frees the skb when enqueue returns this permanent error.
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/ntb/ntb_transport.c
- What this is
- NTB DRIVER COREMAINTAINERS section matched on drivers/ntb/ · ntb@lists.linux.dev · Supported
- Kernel module
- none to look for. The file would have gone into ntb_transport, and Debian does not compile it into that module, so finding ntb_transport in lsmod would say nothing about this CVE.
Check it on the machine
grep -wE 'CONFIG_NTB|CONFIG_NTB_TRANSPORT' /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 switches
- CONFIG_NTB, CONFIG_NTB_TRANSPORT
- Reads as
- all on means the file is compiled; any one off means it is not.
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
- 2026-09-11 (37 days 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/ntb
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 3.9 | 5.10.270 | 4890152a3069 |
| 3.9 | 5.15.221 | 668aa3238548 |
| 3.9 | 6.1.188 | 9b0fa8a9e105 |
| 3.9 | 6.6.157 | b6db88cde0fb |
| 3.9 | 6.12.109 | a7f22105a7df |
| 3.9 | 6.18.50 | 6b6bbc6c878d |
| 3.9 | 7.2.4 | 75a604e9f1cf |
| 3.9 | 7.3 | a4f2387db6f1 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | 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
- ntb_transport_tx_enqueue() is reached from ntb_netdev_start_xmit() on the NTB virtual Ethernet device; in dual-controller/cluster deployments that interconnect carries routed or 802.1Q traffic, so a remote peer can induce full-MTU egress (software VLAN insertion adds VLAN_HLEN past the transport payload limit) without local access.
- AC:LAttack complexity, low
- Any TX buffer longer than tx_max_frame minus the payload header deterministically takes the oversized path; VLAN devices default to the lowerdev MTU so tagged full-size frames always exceed the limit, and AF_PACKET allows MTU+VLAN_HLEN, with no race or uncontrolled layout.
- PR:NPrivileges required, none
- The netdev TX path has no authentication or capability check; once the NTB link is up, any host exchanging traffic over the interconnect or a VLAN/service on it can cause oversized transmits without credentials on the victim.
- UI:NUser interaction, none
- Oversized frames are transmitted by the kernel networking stack during ordinary packet egress; no victim action such as mounting a device or opening a file is required.
- S:UScope, unchanged
- The defect leaks sk_buff memory on the transmitting host inside the same kernel authority; it is not a VM escape, IOMMU/DMA bypass, or corruption of the peer host over the NTB link.
- C:NConfidentiality impact, none
- The oversized path never copies payload bytes and does not free or reuse the skb, so there is no out-of-bounds read, use-after-free, or other information-disclosure primitive.
- I:NIntegrity impact, none
- ntb_process_tx() refuses to DMA or memcpy an oversized buffer and only invokes the completion callback with a NULL pointer, so there is no out-of-bounds write, heap corruption, or control-flow hijacking.
- A:HAvailability impact, high
- Enqueue returns success while the TX handler is called with a NULL skb and skips kfree, permanently leaking one sk_buff (and its pages/socket accounting) per oversized transmit; repeating this exhausts kernel memory and causes OOM denial of service.