Look up another CVE · open CVE-2026-31663 in the interactive tracker
CVE-2026-31663
xfrm: hold dev ref until after transport_finish NF_HOOK
Published 2026-04-24 (6 months ago) by the Linux kernel CNA. Subsystem net/ipv4. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-31663 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 | fixedDSA-6355-1 · 2026-06-21 · text | 6.12.94-1 | Update the kernel and reboot. DSA-6355-1 shipped the fix on 2026-06-21, in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 6.19.13-1 | Update the kernel and reboot. Fixed in 6.19.13-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 6.19.13-1 | Update the kernel and reboot. Fixed in 6.19.13-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
After async crypto completes, xfrm_input_resume() calls dev_put() immediately on re-entry before the skb reaches transport_finish. The skb->dev pointer is then used inside NF_HOOK and its okfn, which can race with device teardown. Remove the dev_put from the async resumption entry and instead drop the reference after the NF_HOOK call in transport_finish, using a saved device pointer since NF_HOOK may consume the skb. This covers NF_DROP, NF_QUEUE and NF_STOLEN paths that skip the okfn. For non-transport exits (decaps, gro, drop) and secondary async return points, release the reference inline when async is set.
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/ipv4/xfrm4_input.c
net/ipv6/xfrm6_input.c
net/xfrm/xfrm_input.c
- What this is
- NETWORKING [IPSEC]MAINTAINERS section matched on net/ipv4/xfrm* · netdev@vger.kernel.org · Maintained
Check it on the machine
grep -wE 'CONFIG_INET|CONFIG_XFRM' /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 switches
- CONFIG_INET, CONFIG_XFRM
- 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
- 2026-04-24 (6 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 2.5% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/ipv4
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.15 | 6.12.94 | 4236c30b437b |
| 4.15 | 6.18.23 | 0f451b43c88b |
| 4.15 | 6.19.13 | 5002beda5cac |
| 4.15 | 7.0 | 1c428b038400 |
| 3.2.100 | 0 | 0 |
| 3.16.55 | 0 | 0 |
| 4.14.24 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DSA-6355-1 | 2026-06-21 | trixie 6.12.94-1 | tracker |
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 complete attacker-controlled path requires a local unprivileged user to create a user/net namespace, configure transport-mode XFRM state, send traffic, and tear down the namespace/device in parallel.
- AC:LAttack complexity, low
- The race is attacker-controlled in the user-namespace scenario: the attacker controls packet injection and device/netns teardown and can repeat the sequence reliably.
- PR:LPrivileges required, low
- XFRM and rtnetlink setup require CAP_NET_ADMIN, but these checks are against the network namespace user_ns and are reachable after unshare -Urn by an unprivileged local user.
- UI:NUser interaction, none
- No victim action is required once the attacker can run local code and create the namespace setup.
- S:UScope, unchanged
- The vulnerable component and impacted resource are the kernel itself; this is a standard kernel memory-safety issue rather than a VM or hardware boundary escape.
- C:HConfidentiality impact, high
- This is a net_device use-after-free, and freed kernel heap objects can potentially be reclaimed and abused for kernel memory disclosure.
- I:HIntegrity impact, high
- Use-after-free in kernel networking code can potentially be shaped into control-flow or data-structure corruption, so high integrity impact is appropriate.
- A:HAvailability impact, high
- The issue was reproduced as a KASAN slab-use-after-free in the async XFRM reinject path and can crash the kernel.