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CVE-2026-46181
RDMA/mlx4: Fix mis-use of RCU in mlx4_srq_event()
Published 2026-05-28 (5 months ago) by the Linux kernel CNA. Subsystem drivers/net. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-46181 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 | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | vulnerable | 6.12.113-1 | No fix published anywhere yet, neither in Debian nor upstream for the series trixie tracks. Watch the Debian tracker page for this CVE. Advisories for trixie have historically landed a median of 11 days after publication. |
| Debian 14forky | fixed | 7.0.7-1 | Update the kernel and reboot. Fixed in 7.0.7-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.7-1 | Update the kernel and reboot. Fixed in 7.0.7-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Sashiko points out the radix_tree itself is RCU safe, but nothing ever frees the mlx4_srq struct with RCU, and it isn't even accessed within the RCU critical section. It also will crash if an event is delivered before the srq object is finished initializing. Use the spinlock since it isn't easy to make RCU work, use refcount_inc_not_zero() to protect against partially initialized objects, and order the refcount_set() to be after the srq is fully initialized.
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/ethernet/mellanox/mlx4/srq.c
- What this is
- MELLANOX MLX4 core VPI driverMAINTAINERS section matched on drivers/net/ethernet/mellanox/mlx4/ · netdev@vger.kernel.org · Maintained
- Kernel module
- mlx4_core
Check it on the machine
grep -wE 'CONFIG_ETHERNET|CONFIG_MLX4_CORE|CONFIG_NET_VENDOR_MELLANOX' /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 mlx4_corePrints 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, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormm
- trixieMnot built on armel/rpi
- forky, sidm
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_ETHERNET, CONFIG_MLX4_CORE, CONFIG_NET_VENDOR_MELLANOX
- 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
- 2026-05-28 (5 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.11%, higher than 1.4% 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 |
|---|---|---|
| 4.9 | 6.18.30 | 1e2a44875b6a |
| 4.9 | 7.0.7 | 8b7833f3bce3 |
| 4.9 | 7.1 | c9341307ea16 |
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:LAttack vector, local
- The race's controllable side (SRQ create/destroy) is driven by local user space through the RDMA verbs interface (/dev/infiniband/uverbsN); a purely remote RDMA peer can generate events but cannot control SRQ lifecycle on the target, so exploitation requires local device access.
- AC:LAttack complexity, low
- The attacker drives both sides — repeatedly creating/arming/destroying SRQs while keeping them at their limit watermark to make events fire — so the UAF/partial-init race is winnable through repetition rather than depending on conditions outside the attacker's control.
- PR:LPrivileges required, low
- Creating/destroying SRQs requires access to the RDMA device node but not root or CAP_SYS_ADMIN; unprivileged users routinely have such access under the user-space RDMA model, so low privileges suffice.
- UI:NUser interaction, none
- The attacker performs all SRQ allocation, arming, and teardown themselves; no action by another user is required.
- S:UScope, unchanged
- The use-after-free and any resulting corruption stay within the kernel's own security authority; no VM/IOMMU/sandbox boundary is crossed.
- C:HConfidentiality impact, high
- A use-after-free lets the attacker reallocate the freed mlx4_srq with controlled contents that are then read (refcount, srq->event pointer), enabling kernel memory disclosure.
- I:HIntegrity impact, high
- The handler performs refcount manipulation and an indirect call through srq->event on freed/reallocated memory, giving a control-flow-hijack / arbitrary-write primitive typical of UAF.
- A:HAvailability impact, high
- Triggering the bug reliably causes a kernel crash — NULL/garbage function-pointer dereference for the partially-initialized case and oops/panic for the use-after-free.