{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-90051", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.783Z", "datePublished": "2026-09-17T16:05:37.620Z", "dateUpdated": "2026-10-19T08:57:09.627Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:57:09.627Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: reject non zerocopy devmem tx\n\nDevmem tcp tx doesn't work without zero-copy, however it's not currently\nenforced if NETIF_F_SG isn't present. In this case, tcp_sendmsg_locked()\nwill try the copy path and try to copy data from an iovec which consists\nof offsets into the dma-buf and would normally fail. Moreover,\nd9c56501c72fd (\"net: tcp: block mixing readable and unreadable frags\")\nrelies on that and assumes that the devmem binding is present IFF we're\nusing the zero-copy path, which can be used to mix net-iov and pages in\na single skb, and break invariants. Let's reject devmem tx without\nzero-copy.\n\nNote, the parameter check the patch is modifying is too loose, we can\ncreate an io_uring request with dmabuf_id and all ZC flags, but which\nwon't have the binding. We replace it with stricter validation." } ], "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 triggering input is local sendmsg or io_uring IORING_OP_SENDMSG_ZC into tcp_sendmsg_locked(): SO_ZEROCOPY, MSG_ZEROCOPY, and an SCM_DEVMEM_DMABUF cmsg that sets sockc.dmabuf_id. A remote TCP peer never supplies that cmsg or those send flags; it only receives the resulting segments.\nAC:L - The attacker drives both sendmsg calls: a MSG_ZEROCOPY+SCM_DEVMEM_DMABUF send queues net-iov (unreadable) frags, then a later sendmsg with sockc.dmabuf_id while zc==0 (sk_route_caps lacks NETIF_F_SG, so the copy path runs with binding set) appends pages onto that skb. MSG_MORE retains the write-queue tail; no victim race is required.\nPR:L - NETDEV_CMD_BIND_TX has no GENL_ADMIN_PERM, and SO_ZEROCOPY plus __sock_cmsg_send(SCM_DEVMEM_DMABUF) have no capability checks. An unprivileged user can bind a TX dmabuf and reach the zc/binding check in tcp_sendmsg_locked; any extra CAP_NET_ADMIN is only the user-namespace kind.\nUI:N - The attacker enables SO_ZEROCOPY, binds a dmabuf via netdev-genl NETDEV_CMD_BIND_TX, and issues the crafted sendmsg/IORING_OP_SENDMSG_ZC sequence on their own TCP socket; no victim mount, open, or other interactive action is required.\nS:U - Mixing net_iov and page frags corrupts skb/TX processing on the sending host inside tcp_sendmsg_locked and later frag walkers. It does not cross a VM/guest or IOMMU authority; __skb_frag_dma_map still classifies each frag with skb_frag_is_net_iov.\nC:H - A mixed skb keeps skb->unreadable from skb_add_rx_frag_netmem while the zc==0 path adds page frags via skb_fill_page_desc. Walkers such as tcp_md5_hash_skb_data use skb_frag_foreach_page/skb_frag_page() on net_iovs (NULL) and kmap that pointer, enabling kernel memory disclosure.\nI:H - Appending sk_page_frag pages onto a net-iov skb via the zc==0 copy path in tcp_sendmsg_locked is frag-type confusion: TX, refcount, and skb_fill_page_desc versus skb_add_rx_frag_netmem cannot treat mixed backing consistently, which yields corrupted skb metadata and write or control-flow primitives.\nA:H - Mixed readable/unreadable frags blow up down the stack: skb_copy_bits/skb_checksum hit WARN_ON_ONCE(!skb_frags_readable), splice hits WARN_ON_ONCE(!skb_frag_page), and kmap of a NULL net_iov page oopses or panics the kernel." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv4/tcp.c" ], "versions": [ { "version": "bd61848900bff597764238f3a8ec67c815cd316e", "lessThan": "2151b2bcf6fcec52665f606eed20da068447f0b7", "status": "affected", "versionType": "git" }, { "version": "bd61848900bff597764238f3a8ec67c815cd316e", "lessThan": "b04326c7927af7048fd4e730f5770cca350d0a60", "status": "affected", "versionType": "git" }, { "version": "bd61848900bff597764238f3a8ec67c815cd316e", "lessThan": "125755776bc6d4dd53eaf551c87e3d460625d638", "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/ipv4/tcp.c" ], "versions": [ { "version": "6.16", "status": "affected" }, { "version": "0", "lessThan": "6.16", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.52", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.6", "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": "6.16", "versionEndExcluding": "6.18.52" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "7.2.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/2151b2bcf6fcec52665f606eed20da068447f0b7" }, { "url": "https://git.kernel.org/stable/c/b04326c7927af7048fd4e730f5770cca350d0a60" }, { "url": "https://git.kernel.org/stable/c/125755776bc6d4dd53eaf551c87e3d460625d638" } ], "title": "tcp: reject non zerocopy devmem tx", "x_generator": { "engine": "bippy-1.2.0" } } } }