Look up another CVE · open CVE-2026-89481 in the interactive tracker
CVE-2026-89481
nvme-tcp: fix host memory disclosure on R2T for a read command
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem drivers/nvme. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89481 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
nvme_tcp_handle_r2t() does not check the direction of the request the R2T refers to. A malicious controller can send an R2T for a READ and the host will answer it: nvme_tcp_setup_h2c_data_pdu() builds the H2CData header and nvme_tcp_try_send_data() sends the request's data buffer. That buffer is the READ destination, so its contents go to the controller. The command then completes normally and nothing is logged. Against a test controller that answers every READ with an R2T, a 4096 byte buffered read returned all 4096 bytes, split over two R2Ts. The pages contained stale kernel data, including an array of struct page pointers. Reject an R2T for a request that is not a write.
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/nvme/host/tcp.c
- What this is
- NVM EXPRESS DRIVERMAINTAINERS section matched on drivers/nvme/host/ · linux-nvme@lists.infradead.org · Supported
- Kernel module
- nvme_tcp
Check it on the machine
grep -w CONFIG_NVME_TCP /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.
lsmod | grep -w nvme_tcpPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sid, bookworm · linux-6.12m
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_NVME_TCP
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:H/I:N/A:Nsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.41%, higher than 34.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/nvme
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.0 | 6.1.188 | 49a4dcf57608 |
| 5.0 | 6.6.157 | bc4013c7cce5 |
| 5.0 | 6.12.109 | a4c3c7310156 |
| 5.0 | 6.18.50 | 3b3d27670c0c |
| 5.0 | 7.2.4 | 3a0b05145053 |
| 5.0 | 7.3 | 6efbc52237fa |
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
- The bug is in the NVMe-over-TCP host PDU receive path (nvme_tcp_recv_skb → nvme_tcp_handle_r2t). A remote NVMe-oF target or on-path attacker sends an R2T PDU over TCP (port 4420) and the host splices the READ destination buffer back over that socket.
- AC:LAttack complexity, low
- A malicious controller that replies to an in-flight READ with a well-formed R2T always triggers the leak; the reporter reproduced a full 4096-byte disclosure with a test target. No race, special memory layout, or rare config beyond CONFIG_NVME_TCP is required.
- PR:NPrivileges required, none
- NVMe/TCP requires no authentication by default (TLS and DH-HMAC-CHAP are optional and off in stock configs), so the remote peer needs no privileges or credentials on the victim host; it simply answers I/O the host is already sending.
- UI:NUser interaction, none
- No victim action is required at exploit time; once the host is connected (including via nvmf-autoconnect at boot), ordinary filesystem or block I/O issues READ commands and the malicious target triggers the leak by replying with R2T PDUs.
- S:UScope, unchanged
- The disclosure is of the host kernel's own I/O buffers and page-cache pages to the connected target. No VM, IOMMU, or sandbox boundary is crossed.
- C:HConfidentiality impact, high
- nvme_tcp_try_send_data() splices the READ destination pages to the attacker. Those pages hold stale kernel memory (reproduced: 4096 bytes including struct page pointers). Every subsequent READ can leak another MDTS-sized buffer of recycled kernel pages.
- I:NIntegrity impact, none
- The host only transmits existing buffer contents; the bug does not write attacker-controlled data into kernel memory, corrupt kernel structures, or provide a write or control-flow hijack primitive.
- A:NAvailability impact, none
- The malformed R2T path completes the command successfully with nothing logged; the reporter observed a silent disclosure with no oops, panic, hang, or other availability impact.