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CVE-2026-64124
net: devmem: reject dma-buf bind with non-page-aligned size or SG length
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem net/core. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-64124 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 | 7.0.12-1 | 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
net_devmem_bind_dmabuf() trusts dmabuf->size and sg_dma_len() to be PAGE_SIZE multiples without checking: - tx_vec is sized dmabuf->size / PAGE_SIZE, and net_devmem_get_niov_at() only bounds-checks virt_addr < dmabuf->size before indexing tx_vec[virt_addr / PAGE_SIZE]. With size = N*PAGE_SIZE + r (1 <= r < PAGE_SIZE), sendmsg() at iov_base = N*PAGE_SIZE passes the bound check and reads tx_vec[N] -- one past. - owner->area.num_niovs = len / PAGE_SIZE while gen_pool_add_owner() covers the full byte len, so a non-page-multiple non-final sg desyncs num_niovs from the gen_pool region for every later sg, on both RX and TX. dma-buf does not require page-aligned sizes, so the bind path has to enforce what its own indexing assumes. Reject both with -EINVAL. The size check is TX-only (only tx_vec is sized off dmabuf->size); the SG-length check covers both directions.
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/core/devmem.c
- What this is
- NETWORKING [GENERAL]MAINTAINERS section matched on net/ · netdev@vger.kernel.org · Maintained
Check it on the machine
grep -w CONFIG_NET_DEVMEM /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 with an answer below compiles the affected file into the kernels it ships. The build rule could not be established for 1 release, so nothing is claimed about those.
- bookworm?
- trixie, forky, sidy
- ?
- not established - no Makefile entry for the affected file
- y
- built into the kernel image on every flavour - only a patch removes it
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.
- Build switch
- CONFIG_NET_DEVMEM
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
- 8.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/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
- net/core
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.16 | 6.18.35 | 134c517dfa63 |
| 6.16 | 7.0.11 | d5008e4e4ee6 |
| 6.16 | 7.1 | 4eb82ba54342 |
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
- Exploitation requires local syscalls—NETLINK_GENERIC netdev bind operations and sendmsg/recvmsg on TCP sockets—not remote packet delivery. Network traffic can trigger RX allocations only after a local bind with a malformed dmabuf.
- AC:LAttack complexity, low
- The attacker fully controls dmabuf size/SG layout at bind time and the virtual offset passed via sendmsg iovec bases, allowing reliable out-of-bounds indexing without races or victim-dependent timing.
- PR:LPrivileges required, low
- TX bind intentionally lacks admin-perm; RX bind requires CAP_NET_ADMIN, which is obtainable in user namespaces via unshare. No real-root privileges are needed, only a local authorized user on a devmem-capable system.
- UI:NUser interaction, none
- No victim interaction is required; the attacker triggers the bug through their own netlink bind and socket operations.
- S:CScope, changed
- Corrupted net_iov metadata can program incorrect DMA addresses for NIC DMA operations, potentially impacting device memory outside the kernel's security authority—a DMA boundary crossing inherent to the devmem subsystem.
- C:HConfidentiality impact, high
- Out-of-bounds read of tx_vec leaks adjacent kernel heap contents (kernel pointers), and heap corruption from misindexed niovs arrays can be leveraged for arbitrary memory disclosure.
- I:HIntegrity impact, high
- Out-of-bounds writes to the niovs array corrupt adjacent kernel heap objects, and use of attacker-influenced pointers in skb fragment setup enables memory corruption exploitable for control-flow hijacking.
- A:HAvailability impact, high
- Dereferencing corrupted net_iov pointers or corrupting heap metadata via out-of-bounds access can cause kernel oops, panic, or hang during TX sendmsg or RX packet processing.