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CVE-2026-89969
nvmet-tcp: fix out-of-bounds write when receiving an over-long PDU
Published 2026-09-16 (33 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-2026-89969 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
nvmet_tcp_try_recv_pdu() reads a PDU header into the fixed 128-byte queue->pdu union, then computes the remaining payload length as queue->left = hdr->hlen - queue->offset + hdgst; and reads that many more bytes into &queue->pdu + queue->offset, without ever bounding the result against sizeof(queue->pdu). A struct nvme_tcp_icreq_pdu is itself 128 bytes, exactly the size of the union. Once a header digest has been negotiated (hdgst = 4), a second ICReq passes the hlen == nvmet_tcp_pdu_size() check but yields queue->left = 128 - 8 + 4 = 124, so bytes 8..132 are written into the 128-byte buffer -- 4 bytes past its end, over queue->hdr_digest and queue->data_digest. Those bytes are attacker-controlled (an ICReq carries no digest), and the duplicate ICReq is only rejected later, after the overflow. A remote unauthenticated host can thus corrupt kernel memory adjacent to the receive buffer. Reject any PDU whose declared length would read past the end of queue->pdu before the second recv.
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/target/tcp.c
- What this is
- NVM EXPRESS TARGET DRIVERMAINTAINERS section matched on drivers/nvme/target/ · linux-nvme@lists.infradead.org · Supported
- Kernel module
- nvmet_tcp
Check it on the machine
grep -w CONFIG_NVME_TARGET_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 nvmet_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_TARGET_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
- 2026-09-16 (33 days ago)source
- CVSS
- 9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.71%, higher than 52.8% 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 | 5.10.270 | a3f0bcfbaf33 |
| 5.0 | 5.15.221 | 4f84d42c53c4 |
| 5.0 | 6.1.188 | 58dc6035b79c |
| 5.0 | 6.6.157 | cf5f39d2b58f |
| 5.0 | 6.12.110 | 3a385e0c39ef |
| 5.0 | 6.18.51 | dbc4acbdb3ca |
| 5.0 | 7.2.5 | d95d342bc0ea |
| 5.0 | 7.3 | 14cc5a7e7773 |
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 flaw is in nvmet-tcp, an in-kernel NVMe-over-TCP target that accepts remote TCP connections; nvmet_tcp_try_recv_pdu() copies attacker-controlled PDU bytes from the socket, so the overflow is reachable from any network peer that can connect to an exposed NVMe-oF TCP port (typical cloud/storage-server deployment).
- AC:LAttack complexity, low
- The attacker enables header digest in the first ICReq (the target copies the initiator's digest flags with no extra configuration), then sends a second 128-byte ICReq; queue->left becomes 124 and four attacker-controlled bytes are written past queue->pdu with no race or condition outside attacker control.
- PR:NPrivileges required, none
- The overflow fires on a duplicate ICReq after TCP accept and digest negotiation, before NVMe Connect, host NQN allow-list, or DH-HMAC-CHAP in-band authentication; no Linux credentials or capabilities on the target are required.
- UI:NUser interaction, none
- Exploitation requires only attacker-sent NVMe/TCP PDUs to an already listening target port; no victim user action such as mounting a filesystem or opening a device is needed.
- S:UScope, unchanged
- The out-of-bounds write corrupts fields of the host's nvmet_tcp_queue in kernel memory and does not cross a VM, hypervisor, container, or IOMMU security boundary.
- C:HConfidentiality impact, high
- Attacker-controlled 4-byte overflow into kernel memory adjacent to queue->pdu is memory corruption that, per kernel guidance, can be leveraged for information disclosure (including by clearing hdr_digest so later verify_hdgst is skipped and by controlling the persisted digest-flag bytes).
- I:HIntegrity impact, high
- This is an attacker-controlled out-of-bounds write past the 128-byte queue->pdu union into adjacent kernel fields (hdr_digest and data_digest); per kernel guidance an OOB write is High integrity impact and can disable PDU digest verification before the duplicate ICReq is rejected.
- A:HAvailability impact, high
- After the overflow, nvmet_tcp_done_recv_pdu() returns -EPROTO and nvmet_tcp_socket_error() calls nvmet_ctrl_fatal_error() once a controller exists (e.g. after unauthenticated Discovery Connect), taking down the NVMe target; the kernel memory corruption can also oops, and the trigger is remotely repeatable.