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CVE-2026-63987
ethtool: coalesce: cap profile updates at NET_DIM_PARAMS_NUM_PROFILES
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem net/ethtool. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-63987 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 | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
ethnl_update_profile() walks the ETHTOOL_A_PROFILE_IRQ_MODERATION nest list with an index 'i' and writes new_profile[i++] without bounding i. The destination is kmemdup()'d at NET_DIM_PARAMS_NUM_PROFILES entries (5), but the Netlink nest count is entirely user-controlled. Netlink policies do not have support for constraining the number of nested entries (or number of multi-attr entries).
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.
net/ethtool/coalesce.c
- What this is
- NETWORKING [ETHTOOL]MAINTAINERS section matched on net/ethtool/
Check it on the machine
grep -w CONFIG_ETHTOOL_NETLINK /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 builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sidy
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switch
- CONFIG_ETHTOOL_NETLINK
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
- 2026-07-19 (3 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
- 0.13%, higher than 2.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- net/ethtool
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.11 | 6.12.93 | d4c9cc7c4778 |
| 6.11 | 6.18.35 | 0c02c190bcd9 |
| 6.11 | 7.0.12 | 6205f7166d2d |
| 6.11 | 7.1 | 7281b096b072 |
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 reached only through the ETHTOOL_MSG_COALESCE_SET generic-netlink ioctl path (ethnl_default_set_doit → ethnl_set_coalesce → ethnl_update_profile), not via remote network packets or physical bus access.
- AC:LAttack complexity, low
- An attacker with CAP_NET_ADMIN can send a crafted netlink message with more than five nested ETHTOOL_A_PROFILE_IRQ_MODERATION attributes and deterministically trigger a heap buffer overflow past the five-entry kmemdup buffer.
- PR:LPrivileges required, low
- ETHTOOL_MSG_COALESCE_SET is gated by GENL_UNS_ADMIN_PERM, which requires CAP_NET_ADMIN in the socket's network namespace user namespace; this capability is obtainable by an unprivileged user via user namespaces (unshare -Urn) or containers granted NET_ADMIN (e.g., hostNetwork pods).
- UI:NUser interaction, none
- Exploitation requires only the attacker's own ethtool netlink SET_COALESCE request with a malformed profile nest; no action by another user or victim is needed.
- S:UScope, unchanged
- The vulnerability corrupts kernel heap memory within the same kernel security domain; it does not by itself cross a VM, container, or IOMMU boundary to affect a separate security authority.
- C:HConfidentiality impact, high
- The out-of-bounds writes past the 120-byte (5 × 24-byte dim_cq_moder) kmalloc allocation can corrupt adjacent slab objects, providing a standard heap-corruption primitive that can be leveraged for arbitrary kernel memory disclosure.
- I:HIntegrity impact, high
- The attacker fully controls the overflowed u16 profile fields (usec, pkts, comps) written beyond the allocation boundary, enabling heap metadata or adjacent-object corruption that can be developed into arbitrary kernel write or code execution.
- A:HAvailability impact, high
- Heap corruption from unbounded profile indexing can cause immediate kernel oops/panic during the write or when the corrupted profile is subsequently used by DIM/virtio-net interrupt moderation paths.