CVE-2026-74336: wifi: mac80211: bound S1G TIM PVB walk to the TIM element

From: Greg Kroah-Hartman <[email protected]>

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

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

wifi: mac80211: bound S1G TIM PVB walk to the TIM element

ieee80211_s1g_check_tim() parses the S1G Partial Virtual Bitmap (PVB) of a
received TIM element. The TIM is handed in as the element payload:
ieee802_11_parse_elems_full() stores elems->tim = elem->data and
elems->tim_len = elem->datalen (net/mac80211/parse.c), so the valid bytes
are [tim, tim + tim_len).

When walking the encoded blocks the function passes the walker an end
sentinel of (const u8 *)tim + tim_len + 2, i.e. two bytes past the end of
the element. ieee80211_s1g_find_target_block() loops while (ptr + 1 <= end)
and dereferences ptr (and the per-mode ieee80211_s1g_len_*() helpers read
*ptr), so it can read up to two bytes beyond the TIM element -- an
out-of-bounds read of adjacent skb/heap data when the TIM is the last
element in the frame. The +2 appears to account for the element id/len
header, but tim already points past that header at the element payload, so
the addend is wrong.

Pass the correct element end, (const u8 *)tim + tim_len.

The Linux kernel CVE team has assigned CVE-2026-74336 to this issue.


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

	Issue introduced in 6.18 with commit e0c47c6229c25b54440fe1f84a0ff533942290b1 and fixed in 7.1.5 with commit 3abc13ec3ac28c343ad7e7b7496e807b924f0edd
	Issue introduced in 6.18 with commit e0c47c6229c25b54440fe1f84a0ff533942290b1 and fixed in 7.2-rc1 with commit b224d18b1e5d1cddfc67f63f41d80023b2ec8889

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-2026-74336
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:
	include/linux/ieee80211-s1g.h


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/3abc13ec3ac28c343ad7e7b7496e807b924f0edd
	https://git.kernel.org/stable/c/b224d18b1e5d1cddfc67f63f41d80023b2ec8889