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CVE-2026-72242
selinux: avoid sk_socket dereference in selinux_sctp_bind_connect()
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem security/selinux. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-72242 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 | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
selinux_sctp_bind_connect() dereferences sk->sk_socket to pass a struct socket * to selinux_socket_bind() and selinux_socket_connect_helper(). However, when the hook is invoked from the ASCONF softirq path (sctp_process_asconf), there is no file reference guaranteeing that sk->sk_socket is non-NULL. The setsockopt callers (bindx, connectx, set_primary, sendmsg connect) hold a file reference and are not affected. Both selinux_socket_bind() and selinux_socket_connect_helper() immediately resolve sock->sk, never using the struct socket * for anything else. Refactor the inner logic into helpers that take a struct sock * directly so that selinux_sctp_bind_connect() never needs to touch sk->sk_socket at all.
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.
security/selinux/hooks.c
- What this is
- SELINUX SECURITY MODULEMAINTAINERS section matched on security/selinux/ · selinux@vger.kernel.org · Supported
Check it on the machine
grep -w CONFIG_SECURITY_SELINUX /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, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormy
- trixieYnot built on armel/rpi
- forky, sidy
- y
- built into the kernel image on every flavour - only a patch removes it
- Y
- built in where it is built at all; some flavours do not build it
- Build switch
- CONFIG_SECURITY_SELINUX
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
- 2026-08-15 (2 months ago)source
- CVSS
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.70%, higher than 52.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- security/selinux
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.17 | 5.10.266 | e4f3b8db1b0c |
| 4.17 | 5.15.217 | 2fcaf133a8fd |
| 4.17 | 6.1.184 | a4bc2fb85364 |
| 4.17 | 6.6.148 | 5d4d93f9bfbc |
| 4.17 | 6.12.97 | cc8bd47b35ec |
| 4.17 | 6.18.40 | d61a80b17254 |
| 4.17 | 7.1.5 | 37d642b37ccd |
| 4.17 | 7.2 | 56acfeb10019 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | 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:NAttack vector, network
- The vulnerable code runs in the SCTP receive softirq path when a remote peer sends an authenticated ASCONF chunk (ADD_IP/SET_PRIMARY) on an existing association; packets enter via sctp_rcv() from the network stack, not local syscalls.
- AC:LAttack complexity, low
- An attacker with an established SCTP association controls ASCONF timing and can flood ADD_IP/SET_PRIMARY during the documented post-close() teardown window when sk_socket is NULL but associations still process shutdown-state packets.
- PR:NPrivileges required, none
- Exploitation requires only the ability to complete a normal SCTP association handshake with a SELinux-protected peer; no Linux capabilities, root, or local shell access are needed to send the triggering ASCONF packets over the network.
- UI:NUser interaction, none
- No victim user action is required beyond normal server operation; the crash is triggered by attacker-sent ASCONF traffic arriving while the kernel processes socket teardown after application close(), not by opening files or clicking links.
- S:UScope, unchanged
- Impact is a kernel NULL pointer dereference panic/oops within the same kernel security domain; it does not cross VM, container, or IOMMU boundaries and is a standard remote denial-of-service against the host kernel.
- C:NConfidentiality impact, none
- The failure mode is a direct NULL pointer dereference of sk->sk_socket before reading sock->sk; there is no use-after-free, out-of-bounds access, or memory corruption that could yield information disclosure.
- I:NIntegrity impact, none
- The bug does not write or corrupt memory; selinux_socket_bind()/connect_helper() crash immediately on the NULL socket pointer without modifying kernel data structures or achieving code execution.
- A:HAvailability impact, high
- Dereferencing a NULL sk_socket in softirq causes a kernel oops/panic, crashing the entire system; this is repeatable whenever ASCONF arrives during the post-close() window on SCTP associations in shutdown states.