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

net: mctp: hold a reference to the route device in mctp_route_lookup()

mctp_route_lookup() uses rt->dev without holding a reference on it.
mctp_route_lookup_single() returns the route under RCU only, so the
route's device can be torn down concurrently: mctp_dev_put() drops the
last reference and synchronously kfree()s mdev->addrs. mctp_dev_saddr()
then reads rt->dev->addrs[0], giving a use-after-free reachable by an
unprivileged local AF_MCTP user on the receive/forwarding path (no
CAP_NET_RAW required):

BUG: KASAN: slab-use-after-free in mctp_route_lookup
Read of size 1 at addr ... by task mctp_uaf/...
mctp_route_lookup
mctp_pkttype_receive
Freed by task ...:
kfree
mctp_dev_put
mctp_dev_notify

In the same window mctp_dst_from_route() -> mctp_dev_hold() also
increments a refcount that has already reached zero
("refcount_t: addition on 0 ... mctp_dev_hold").

This reintroduces the use-after-free class of CVE-2023-3439: the source
address lookup was moved ahead of the point where the destination takes
its device reference.

Take a reference with refcount_inc_not_zero() before touching rt->dev,
skip a device that is already dead, and drop the reference once the
destination has taken its own.

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History

Sat, 12 Sep 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-825
References
Metrics threat_severity

None

cvssV3_1

{'score': 4.7, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate


Fri, 11 Sep 2026 23:45:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: net: mctp: hold a reference to the route device in mctp_route_lookup() mctp_route_lookup() uses rt->dev without holding a reference on it. mctp_route_lookup_single() returns the route under RCU only, so the route's device can be torn down concurrently: mctp_dev_put() drops the last reference and synchronously kfree()s mdev->addrs. mctp_dev_saddr() then reads rt->dev->addrs[0], giving a use-after-free reachable by an unprivileged local AF_MCTP user on the receive/forwarding path (no CAP_NET_RAW required): BUG: KASAN: slab-use-after-free in mctp_route_lookup Read of size 1 at addr ... by task mctp_uaf/... mctp_route_lookup mctp_pkttype_receive Freed by task ...: kfree mctp_dev_put mctp_dev_notify In the same window mctp_dst_from_route() -> mctp_dev_hold() also increments a refcount that has already reached zero ("refcount_t: addition on 0 ... mctp_dev_hold"). This reintroduces the use-after-free class of CVE-2023-3439: the source address lookup was moved ahead of the point where the destination takes its device reference. Take a reference with refcount_inc_not_zero() before touching rt->dev, skip a device that is already dead, and drop the reference once the destination has taken its own.
Title net: mctp: hold a reference to the route device in mctp_route_lookup()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

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cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-09-11T19:42:50.866Z

Reserved: 2026-08-26T14:34:25.812Z

Link: CVE-2026-80995

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-11T20:19:06.497

Modified: 2026-09-11T20:19:06.497

Link: CVE-2026-80995

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-09-11T19:42:50Z

Links: CVE-2026-80995 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-09-12T09:45:11Z

Weaknesses