CVE-2026-80843: xfrm: fix xfrm_state_construct() auth-trunc leak

CVE-2026-80843: xfrm: fix xfrm_state_construct() auth-trunc leak

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

xfrm: fix xfrm_state_construct() auth-trunc leak

attach_auth_trunc() can allocate x->aalg while leaving
x->props.aalgo at zero when the selected auth algorithm has no
sadb_alg_id. One real case is cmac(aes).

xfrm_state_construct() then treats !x->props.aalgo as "no auth
algorithm attached yet" and calls attach_auth(). That overwrites
x->aalg and loses the first allocation. Any later failure or teardown
only frees the replacement pointer.

Check whether x->aalg is already attached instead of inferring that
state from x->props.aalgo.

The Linux kernel CVE team has assigned CVE-2026-80843 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 2.6.33 with commit 4447bb33f09444920a8f1d89e1540137429351b6 and fixed in 5.10.269 with commit 958ae9f261319e1cdc44879886bcda2263258cca
	Issue introduced in 2.6.33 with commit 4447bb33f09444920a8f1d89e1540137429351b6 and fixed in 5.15.220 with commit fb7f3e74789a3c89647f4eb768f6dfaf4a751e72
	Issue introduced in 2.6.33 with commit 4447bb33f09444920a8f1d89e1540137429351b6 and fixed in 6.1.187 with commit ba0c110c205855b3f1e3130d8c0fdb484d704c8c
	Issue introduced in 2.6.33 with commit 4447bb33f09444920a8f1d89e1540137429351b6 and fixed in 6.6.156 with commit c8837bbe792257af547fd1c0252553ce13148795
	Issue introduced in 2.6.33 with commit 4447bb33f09444920a8f1d89e1540137429351b6 and fixed in 6.12.108 with commit 71d42da01740ec6557837bebec0bc48cfc3b4c39
	Issue introduced in 2.6.33 with commit 4447bb33f09444920a8f1d89e1540137429351b6 and fixed in 6.18.49 with commit cf67361e78dca488d6e4df8396a53e6745a3a80e
	Issue introduced in 2.6.33 with commit 4447bb33f09444920a8f1d89e1540137429351b6 and fixed in 7.1.13 with commit 37426395cb90ef217beec8407a14bd82153793d3
	Issue introduced in 2.6.33 with commit 4447bb33f09444920a8f1d89e1540137429351b6 and fixed in 7.2.3 with commit be19d20e53a239572bb2a28efcc1cd2b069b1ef9
	Issue introduced in 2.6.33 with commit 4447bb33f09444920a8f1d89e1540137429351b6 and fixed in 7.3-rc1 with commit c12cbf56320fb633484ee0ca1fb7d68d6b64b213

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-80843
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/xfrm/xfrm_user.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/958ae9f261319e1cdc44879886bcda2263258cca
	https://git.kernel.org/stable/c/fb7f3e74789a3c89647f4eb768f6dfaf4a751e72
	https://git.kernel.org/stable/c/ba0c110c205855b3f1e3130d8c0fdb484d704c8c
	https://git.kernel.org/stable/c/c8837bbe792257af547fd1c0252553ce13148795
	https://git.kernel.org/stable/c/71d42da01740ec6557837bebec0bc48cfc3b4c39
	https://git.kernel.org/stable/c/cf67361e78dca488d6e4df8396a53e6745a3a80e
	https://git.kernel.org/stable/c/37426395cb90ef217beec8407a14bd82153793d3
	https://git.kernel.org/stable/c/be19d20e53a239572bb2a28efcc1cd2b069b1ef9
	https://git.kernel.org/stable/c/c12cbf56320fb633484ee0ca1fb7d68d6b64b213