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CVE-2026-63919
xfrm: input: hold netns during deferred transport reinjection
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem net/xfrm. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-63919 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 | fixed | 6.1.176-1 | Update the kernel and reboot. Fixed in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| 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
Transport-mode reinjection stores a struct net pointer in skb->cb and uses it later from xfrm_trans_reinject(). That pointer must stay valid until the deferred callback runs. Take a netns reference when queueing deferred reinjection work and drop it after the callback completes. Use maybe_get_net() so the queueing path does not revive a namespace that is already being torn down. This keeps the existing workqueue design and fixes the netns lifetime handling in one place for all users of xfrm_trans_queue_net().
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/xfrm/xfrm_input.c
- What this is
- NETWORKING [IPSEC]MAINTAINERS section matched on net/xfrm/ · netdev@vger.kernel.org · Maintained
Check it on the machine
grep -w 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 switch
- CONFIG_XFRM
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:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.65%, higher than 50.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/xfrm
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.6 | 5.10.259 | 7ee59eda8820 |
| 5.6 | 5.15.210 | 2df7059a18af |
| 5.6 | 6.1.176 | 8dfabcba6a94 |
| 5.6 | 6.6.143 | 48ce101cd630 |
| 5.6 | 6.12.93 | 55ddfc41451f |
| 5.6 | 6.18.35 | 9f7ebb45a83a |
| 5.6 | 7.0.12 | 9f67a36e91bb |
| 5.6 | 7.1 | c16f74dc1d75 |
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:NAttack vector, network
- The vulnerable path is reached when IPsec ESP/AH packets are received and processed through xfrm_input transport-mode reinjection, which is a network packet receive path in net/xfrm. Remote peers can send ESP traffic to trigger deferred queueing on systems with IPsec configured.
- AC:LAttack complexity, low
- The attacker controls both sides of the race by flooding IPsec packets to queue deferred reinjection work while concurrently destroying the network namespace, making the UAF reliably triggerable without conditions outside attacker control.
- PR:LPrivileges required, low
- Exploitation requires configuring xfrm/IPsec and managing network namespace lifecycle, both reachable with CAP_NET_ADMIN obtainable by an unprivileged user via user namespaces (unshare -Urn), not requiring real root in the init namespace.
- UI:NUser interaction, none
- No victim user interaction is required; exploitation is achieved through automated packet transmission and namespace teardown scripted by the attacker.
- S:UScope, unchanged
- Impact is kernel memory corruption and potential privilege escalation within the same security authority; this is not a VM escape or cross-authority boundary bypass.
- C:HConfidentiality impact, high
- The deferred callback dereferences a freed struct net (e.g., ip6_rcv_finish_core reads sysctl fields from the UAF pointer), providing an information disclosure primitive from attacker-influenced freed slab memory.
- I:HIntegrity impact, high
- Use-after-free on the large struct net slab object enables heap grooming and memory corruption exploitable for arbitrary kernel writes and control-flow hijacking, not merely a bounded modification.
- A:HAvailability impact, high
- Dereferencing a freed network namespace structure causes kernel oops/panic from the workqueue callback path, and UAF reliably threatens system availability even when full exploitation is not attempted.