CVE-2026-43341: net/ipv6: ioam6: prevent schema length wraparound in trace fill

CVE-2026-43341: net/ipv6: ioam6: prevent schema length wraparound in trace fill

[Greg Kroah-Hartman]

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

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

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

net/ipv6: ioam6: prevent schema length wraparound in trace fill

ioam6_fill_trace_data() stores the schema contribution to the trace
length in a u8. With bit 22 enabled and the largest schema payload,
sclen becomes 1 + 1020 / 4, wraps from 256 to 0, and bypasses the
remaining-space check. __ioam6_fill_trace_data() then positions the
write cursor without reserving the schema area but still copies the
4-byte schema header and the full schema payload, overrunning the trace
buffer.

Keep sclen in an unsigned int so the remaining-space check and the write
cursor calculation both see the full schema length.

The Linux kernel CVE team has assigned CVE-2026-43341 to this issue.


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

	Issue introduced in 5.15 with commit 8c6f6fa6772696be0c047a711858084b38763728 and fixed in 6.1.168 with commit e96d48b37708d53cbdc47f6f60b0714fc4a5f596
	Issue introduced in 5.15 with commit 8c6f6fa6772696be0c047a711858084b38763728 and fixed in 6.6.134 with commit d1b041080086e91d3733a5438a8c51ad5d3d8e09
	Issue introduced in 5.15 with commit 8c6f6fa6772696be0c047a711858084b38763728 and fixed in 6.12.81 with commit 77695a69baca9b99d95fad09fc78c2318736604f
	Issue introduced in 5.15 with commit 8c6f6fa6772696be0c047a711858084b38763728 and fixed in 6.18.22 with commit 184d2e9db27c0f76226b5cad16fe29510a5d2280
	Issue introduced in 5.15 with commit 8c6f6fa6772696be0c047a711858084b38763728 and fixed in 6.19.12 with commit d6e1c9b02d85a4f1f4ba6d68e916d9b610a3ed7d
	Issue introduced in 5.15 with commit 8c6f6fa6772696be0c047a711858084b38763728 and fixed in 7.0 with commit 5e67ba9bb531e1ec6599a82a065dea9040b9ce50

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-2026-43341
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/ipv6/ioam6.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/e96d48b37708d53cbdc47f6f60b0714fc4a5f596
	https://git.kernel.org/stable/c/d1b041080086e91d3733a5438a8c51ad5d3d8e09
	https://git.kernel.org/stable/c/77695a69baca9b99d95fad09fc78c2318736604f
	https://git.kernel.org/stable/c/184d2e9db27c0f76226b5cad16fe29510a5d2280
	https://git.kernel.org/stable/c/d6e1c9b02d85a4f1f4ba6d68e916d9b610a3ed7d
	https://git.kernel.org/stable/c/5e67ba9bb531e1ec6599a82a065dea9040b9ce50