{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-80995", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-26T14:34:25.812Z", "datePublished": "2026-09-11T19:42:50.866Z", "dateUpdated": "2026-10-19T08:46:19.571Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:46:19.571Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: mctp: hold a reference to the route device in mctp_route_lookup()\n\nmctp_route_lookup() uses rt->dev without holding a reference on it.\nmctp_route_lookup_single() returns the route under RCU only, so the\nroute's device can be torn down concurrently: mctp_dev_put() drops the\nlast reference and synchronously kfree()s mdev->addrs. mctp_dev_saddr()\nthen reads rt->dev->addrs[0], giving a use-after-free reachable by an\nunprivileged local AF_MCTP user on the receive/forwarding path (no\nCAP_NET_RAW required):\n\n BUG: KASAN: slab-use-after-free in mctp_route_lookup\n Read of size 1 at addr ... by task mctp_uaf/...\n mctp_route_lookup\n mctp_pkttype_receive\n Freed by task ...:\n kfree\n mctp_dev_put\n mctp_dev_notify\n\nIn the same window mctp_dst_from_route() -> mctp_dev_hold() also\nincrements a refcount that has already reached zero\n(\"refcount_t: addition on 0 ... mctp_dev_hold\").\n\nThis reintroduces the use-after-free class of CVE-2023-3439: the source\naddress lookup was moved ahead of the point where the destination takes\nits device reference.\n\nTake a reference with refcount_inc_not_zero() before touching rt->dev,\nskip a device that is already dead, and drop the reference once the\ndestination has taken its own." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The UAF is reached when mctp_pkttype_receive() calls mctp_route_lookup() while the route device is destroyed via mctp_dev_notify()/NETDEV_UNREGISTER. An unprivileged local user can create a TUN (ARPHRD_NONE auto-attaches mctp_dev), inject ETH_P_MCTP frames, and delete that netdev; this is a local syscall/netlink path, not a remote IP service.\nAC:L - The attacker controls both sides of the race by injecting MCTP packets on one thread and unregistering the TUN/MCTP netdev on another, and can retry until mctp_dev_saddr() runs after mctp_dev_put() has synchronously kfree'd mdev->addrs.\nPR:L - TUN creation, MCTP address/route setup, and netdev teardown require CAP_NET_ADMIN, which an unprivileged user obtains in a user+net namespace. The receive/forwarding path has no CAP_NET_RAW check, unlike mctp_sendmsg().\nUI:N - Exploitation requires no victim action; the attacker alone creates the interface, injects frames, and tears it down.\nS:U - Impact is in-kernel use-after-free and local privilege escalation within the same kernel security authority; no VM escape, IOMMU bypass, or sandbox boundary is crossed.\nC:H - This is a use-after-free of mdev->addrs (and a dangling mctp_dev after refcount-add-on-0); UAF of a kmalloc object enables heap reuse and arbitrary kernel memory disclosure.\nI:H - After the last reference is dropped, mctp_dst_from_route() still calls mctp_dev_hold() and later dst.output() uses the freed device; reclaiming that object yields an arbitrary write and control-flow hijack primitive.\nA:H - KASAN reports a slab-use-after-free in mctp_route_lookup and a refcount_t addition-on-0 in mctp_dev_hold; the UAF reliably oopses or panics the kernel even when not fully exploited." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/mctp/route.c" ], "versions": [ { "version": "22cb45afd221b9e4f2a1dcc74a8ff645b7293aa1", "lessThan": "cc561f8af25586300c2f9d285babb163b866b293", "status": "affected", "versionType": "git" }, { "version": "22cb45afd221b9e4f2a1dcc74a8ff645b7293aa1", "lessThan": "408da1df18116c971c3392e21e50586688cd3fbf", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/mctp/route.c" ], "versions": [ { "version": "7.1", "status": "affected" }, { "version": "0", "lessThan": "7.1", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.1", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.1", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/cc561f8af25586300c2f9d285babb163b866b293" }, { "url": "https://git.kernel.org/stable/c/408da1df18116c971c3392e21e50586688cd3fbf" } ], "title": "net: mctp: hold a reference to the route device in mctp_route_lookup()", "x_generator": { "engine": "bippy-1.2.0" } } } }