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CVE-2026-74627
net: devmem: prevent net-iov / page mixing
Published 2026-08-22 (2 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-2026-74627 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 | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
We should either have net_iov or page backed frags in a single skb, otherwise it blows up down the stack. Don't allow mixing in zerocopy_fill_skb_from_devmem().
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/datagram.c
- What this is
- NETWORKING [GENERAL]MAINTAINERS section matched on net/ · netdev@vger.kernel.org · Maintained
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
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 Debian linux-config packages
Signals
- Published
- 2026-08-22 (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
- 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 | 6.18.45 | e9bfe12b1d04 |
| 6.16 | 7.1.9 | ed08011ae0be |
| 6.16 | 7.2 | 53a43508ee33 |
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 in zerocopy_fill_skb_from_devmem() reached only via local sendmsg() on TCP sockets (tcp_sendmsg_locked -> skb_zerocopy_iter_stream -> __zerocopy_sg_from_iter); remote peers cannot invoke this skb construction path without local process cooperation.
- AC:LAttack complexity, low
- An attacker reliably triggers mixing by partially filling the TCP write-queue tail skb with page-backed zerocopy or copy data, then issuing MSG_ZEROCOPY+SCM_DEVMEM_DMABUF sendmsg on the same skb; no race or uncontrollable layout is required.
- PR:LPrivileges required, low
- Exploitation requires SOCK_ZEROCOPY, netdev-genl NETDEV_CMD_BIND_TX dmabuf binding, and a netmem_tx-capable NIC; CAP_NET_ADMIN for netdev/dmabuf setup is obtainable inside user/network namespaces via unshare without init-namespace root.
- UI:NUser interaction, none
- No victim file open, mount, or interactive action is needed; the attacker configures devmem TX binding and drives the crafted sendmsg sequence on their own TCP socket.
- S:UScope, unchanged
- Impact is kernel frag-type confusion and faults during local TX processing on the same host; it does not cross VM, container, or IOMMU security boundaries to a different authority.
- C:HConfidentiality impact, high
- Mixing page-backed and net_iov frags violates skb unreadability invariants; downstream frag walkers that assume uniform backing can dereference invalid pages via skb_frag_foreach_page, enabling kernel memory disclosure primitives.
- I:HIntegrity impact, high
- Creating an skb with both page and net_iov fragments is explicit frag-type confusion; the stack cannot safely manage mixed backing types, and corrupted skb metadata/refcounts can be leveraged for arbitrary kernel writes or control-flow hijacking.
- A:HAvailability impact, high
- The fix commit states mixed frags blow up down the stack; malformed skbs reaching TX, checksum, GSO, or frag-unref paths can trigger kernel oops/panic on netmem_tx deployments (cloud/HPC mlx5, bnxt, gve hosts).