CVE-2026-80995
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk2th percentile - higher than 2% of all known CVEs
Summary
In the Linux kernel, mctp_route_lookup() uses rt->dev without holding a reference, and mctp_route_lookup_single() returns the route under RCU only. The route's device can be torn down concurrently, leading to a use-after-free in mctp_dev_saddr() when reading rt->dev->addrs[0], reachable by an unprivileged local AF_MCTP user without CAP_NET_RAW. In the same window mctp_dev_hold() increments a refcount that has already reached zero.
Risk Assessment
A use-after-free vulnerability can lead to privilege escalation or arbitrary code execution in kernel context by a local user. The risk is high because it requires neither CAP_NET_RAW nor remote access.
Recommendation
Update the Linux kernel to a version containing the fix that uses refcount_inc_not_zero() before touching rt->dev, skips a dead device, and drops the reference once the destination has taken its own. Until then, restrict local user access to AF_MCTP sockets.
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Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS