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CVE-2026-53389
net/tcp-ao: fix use-after-free of key in del_async path
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem net/ipv4. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-53389 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 | fixed | 6.12.95-1 | Update the kernel and reboot. Fixed in 6.12.95-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.3-1 | Update the kernel and reboot. Fixed in 7.1.3-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.3-1 | Update the kernel and reboot. Fixed in 7.1.3-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
In tcp_ao_delete_key(), the del_async path skips the current_key and rnext_key validity checks present in the synchronous path, assuming these pointers are always NULL on LISTEN sockets. However, if a key was added with set_current=1/set_rnext=1 while the socket was in CLOSE state, current_key and rnext_key will be non-NULL after listen() transitions the socket to LISTEN. When such a key is deleted with del_async=1, hlist_del_rcu() and call_rcu() free the key without clearing the dangling pointers. After the RCU grace period, getsockopt(TCP_AO_INFO) dereferences current_key->sndid and rnext_key->rcvid from freed slab memory. Clear current_key and rnext_key in the del_async path when they reference the key being deleted.
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/tcp_ao.c
- What this is
- NETWORKING [TCP]MAINTAINERS section matched on net/ipv4/tcp*.c · netdev@vger.kernel.org · Maintained
Check it on the machine
grep -wE 'CONFIG_INET|CONFIG_TCP_AO' /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 does not build this code in 1 release. It does build it in 2 releases, so the answer depends on which release the machine runs. The build rule could not be established for 1 release, so nothing is claimed about those.
- bookworm?
- trixien
- forky, sidYnot built on armhf/armmp, armhf/armmp-lpae
- ?
- not established - no Makefile entry for the affected file
- n
- not enabled on any flavour - this release does not build the code
- Y
- built in where it is built at all; some flavours do not build 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 switches
- CONFIG_INET, CONFIG_TCP_AO
- 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
- 2026-07-19 (3 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
- unimportantsource
- 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 |
|---|---|---|
| 6.7 | 6.12.95 | 6ce7ef417437 |
| 6.7 | 6.18.38 | e77fbefd1269 |
| 6.7 | 7.1.3 | 7ddc29a094d9 |
| 6.7 | 7.2 | 5ba9950bc907 |
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 `setsockopt`/`getsockopt` syscalls on a TCP socket owned by the attacker; the UAF is triggered in socket-option management, not by remote TCP-AO packet processing on the listen path.
- AC:LAttack complexity, low
- An attacker who controls the socket can deterministically perform add-with-set_current/set_rnext on CLOSE, listen(), del_async delete, wait for RCU, then getsockopt(TCP_AO_INFO) without depending on conditions outside their control.
- PR:LPrivileges required, low
- No capability checks protect TCP-AO socket options beyond socket ownership; an unprivileged local user (including in a user namespace) can create a listening TCP socket, configure TCP-AO keys, and trigger the bug on their own socket.
- UI:NUser interaction, none
- No victim interaction is required; the attacker drives the full exploit sequence through their own socket file descriptor.
- S:UScope, unchanged
- Impact is confined to kernel memory corruption and privilege escalation within the same security domain; this is not a cross-VM, cross-container, or IOMMU boundary escape.
- C:HConfidentiality impact, high
- The bug is a use-after-free where `getsockopt(TCP_AO_INFO)` reads `sndid`/`rcvid` from freed `tcp_ao_key` slab memory, enabling information disclosure from attacker-influenced freed heap contents.
- I:HIntegrity impact, high
- Use-after-free of a heap-allocated `tcp_ao_key` structure can be leveraged with heap grooming for arbitrary memory corruption and potential kernel code execution, not merely a bounded write.
- A:HAvailability impact, high
- Dereferencing freed kernel memory via `getsockopt(TCP_AO_INFO)` can cause kernel oops/panic and denial of service even when full exploitation is not attempted.