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CVE-2026-72345
net/mlx5: LAG, Fix off-by-one in single-FDB error rollback
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem drivers/net. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-72345 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
On failure at index i, the reverse cleanup loop in mlx5_lag_create_single_fdb() starts from i, so the failed index itself is rolled back. That can operate on uninitialized state or double-tear-down a rule the add_one path already self-rolled-back. Start the rollback from i - 1 so only successfully-installed entries are undone.
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/mlx5/core/lag/shared_fdb.c
- What this is
- MELLANOX MLX5 core VPI driverMAINTAINERS section matched on drivers/net/ethernet/mellanox/mlx5/core/ · netdev@vger.kernel.org · Maintained
Show whether Debian builds this, per release
Not established. This site could not find the build rule for the affected file in the kernel trees Debian ships, so it has no answer about whether Debian compiles this code. Read that as unknown, never as absent.
- bookworm, trixie, forky, sid?
- ?
- not established - no Makefile entry for the affected file
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
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
Signals
- Published
- 2026-08-15 (2 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
- 0.17%, higher than 6.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- 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 |
|---|---|---|
| 6.14 | 6.18.57 | 0be672071d6e |
| 6.14 | 7.1.5 | 40cc06bf7147 |
| 6.14 | 7.2 | 0f0e4ae6975c |
| 6.12.113 | 0 | 0 |
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 bug is only reachable when mlx5 shared-FDB LAG setup runs via local admin paths (bond netdev notifier or devlink esw_multiport), not from remote packet handling on the mlx5 data path.
- AC:LAttack complexity, low
- An attacker with CAP_NET_ADMIN can trigger bonding/MPESW setup and retry until mlx5_eswitch_offloads_single_fdb_add_one fails, reliably exercising the faulty rollback loop without uncontrollable timing or layout dependencies.
- PR:LPrivileges required, low
- Exploitation requires configuring bonding or devlink eswitch parameters, which needs CAP_NET_ADMIN; per kernel CNA guidance this is Low because that capability is obtainable inside unprivileged user namespaces.
- UI:NUser interaction, none
- No end-user interaction is required beyond the attacker (or their privileged account) performing the LAG/shared-FDB configuration that reaches mlx5_lag_create_single_fdb().
- S:UScope, unchanged
- Impact is confined to kernel mlx5 eswitch/LAG state on the host; it does not cross a VM, container, or IOMMU security boundary into another authority.
- C:HConfidentiality impact, high
- The off-by-one rollback can tear down uninitialized or already-cleared eswitch flow/FDB state, causing memory corruption that can be leveraged for kernel information disclosure beyond a simple crash.
- I:HIntegrity impact, high
- Double teardown of master egress bounce rules and slave root FDB entries can corrupt mlx5 steering structures and heap metadata, enabling arbitrary kernel writes or control-flow hijacking.
- A:HAvailability impact, high
- Incorrect rollback of failed single-FDB installs can panic the kernel or leave eswitch offload state inconsistent, causing oops, hang, or denial of service on affected Mellanox hosts.