{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-98368", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.344Z", "datePublished": "2026-10-06T08:46:53.292Z", "dateUpdated": "2026-10-19T09:18:20.253Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T09:18:20.253Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nesp: downgrade zerocopy managed frags before mutating skb frags\n\nOn the out-of-place output path (esp->inplace == false) ESP rewrites the\nskb frag array: esp_output_head() appends a trailer frag and\nesp_output_tail() replaces the frags with a destination page, both\nreferenced with get_page().\n\nWhen the skb carries zerocopy managed frags (SKBFL_MANAGED_FRAG_REFS) the\npayload frags are owned by the ubuf and must not be referenced or\nunreferenced individually, but ESP mutates the frag array without ever\ndowngrading the skb. This breaks the managed-frag invariant two ways:\n\n - esp_ssg_unref() walks the source scatterlist and drops a page\n reference for every frag, including the ubuf-owned payload frags,\n pushing their refcount below the GUP pin bias while the pages are\n still pinned, i.e. a use-after-free of the zerocopy pages;\n\n - esp_output_tail() installs its destination page as frag 0 with\n get_page() but leaves SKBFL_MANAGED_FRAG_REFS set, so\n skb_release_data() takes the skip_unref branch and never drops that\n reference, leaking the x->xfrag page at packet rate.\n\nFix this the way every other frag-mutating site does (__ip_append_data(),\n__ip6_append_data(), tcp_sendmsg_locked()) and call\nskb_zcopy_downgrade_managed() before ESP touches the frag array: it takes\na real reference on each existing frag and clears SKBFL_MANAGED_FRAG_REFS,\nso the per-frag unref in esp_ssg_unref() and the frag release in\nskb_release_data() are both balanced and no mixed-ownership frag array is\nleft behind." } ], "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 - Managed frags are set only by io_uring's io_sg_from_iter() for IORING_OP_SEND_ZC/SENDMSG_ZC with IORING_RECVSEND_FIXED_BUF, so a local process must submit the zerocopy send that esp_output_head()/esp6_output_head() then mutates; a remote peer cannot produce a SKBFL_MANAGED_FRAG_REFS skb.\nAC:L - The attacker picks every input: an uncloned UDP skb whose data_len+tailen fits in a page and lacks tailroom reliably takes the esp->inplace=false branch, then esp_ssg_unref() drops refs on the ubuf-owned frags. No race or outside state is needed.\nPR:L - io_uring zerocopy send needs no privilege. The ESP SA/policy can be added inside an unprivileged user+net namespace because xfrm_user_rcv_msg only checks netlink_net_capable(CAP_NET_ADMIN); on a host with IPsec already set up, any local user's traffic hits it.\nUI:N - The attacker does everything with their own io_uring ring, registered buffer, socket and (namespaced) xfrm state; no other user has to act.\nS:U - The page refcount underflow and the freed page stay inside the kernel's own authority, so this is a normal local privilege escalation with no VM or sandbox boundary crossed.\nC:H - esp_ssg_unref() pushes the pinned registered-buffer pages' refcount below the GUP pin bias, so the page is freed while io_uring still has it mapped; once reallocated (e.g. as page tables or slab) the attacker can read kernel memory through the stale buffer.\nI:H - Writing through the still-registered fixed buffer into the freed and reallocated page is a page-level use-after-free write primitive (Dirty-Pagetable style), enough for arbitrary kernel memory corruption and privilege escalation.\nA:H - The page UAF leads to bad-page/refcount oopses, and the missing put_page on the x->xfrag page installed by esp_output_tail() leaks memory at packet rate; both can take the system down." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv4/esp4.c", "net/ipv6/esp6.c" ], "versions": [ { "version": "753f1ca4e1e50248a1b760c9774d6d6b354562cc", "lessThan": "2359264f377cdbdef2d95868cc8fb572949e48d3", "status": "affected", "versionType": "git" }, { "version": "753f1ca4e1e50248a1b760c9774d6d6b354562cc", "lessThan": "69a768c12398cada8528080332c822623fa7064d", "status": "affected", "versionType": "git" }, { "version": "753f1ca4e1e50248a1b760c9774d6d6b354562cc", "lessThan": "6508304ac2c8cdafca2f4ab915df8c707893e134", "status": "affected", "versionType": "git" }, { "version": "753f1ca4e1e50248a1b760c9774d6d6b354562cc", "lessThan": "6cab554f2c0f28773f712ed3a5479103f42ce844", "status": "affected", "versionType": "git" }, { "version": "753f1ca4e1e50248a1b760c9774d6d6b354562cc", "lessThan": "0d0845ee61c5df47cc68bc446501f48f71e8dcc6", "status": "affected", "versionType": "git" }, { "version": "753f1ca4e1e50248a1b760c9774d6d6b354562cc", "lessThan": "f89416eb3db151170a6f3c6dfc5239d26cdce4d2", "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/esp4.c", "net/ipv6/esp6.c" ], "versions": [ { "version": "6.0", "status": "affected" }, { "version": "0", "lessThan": "6.0", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.189", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.158", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.112", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.54", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.8", "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": "6.0", "versionEndExcluding": "6.1.189" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.0", "versionEndExcluding": "6.6.158" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.0", "versionEndExcluding": "6.12.112" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.0", "versionEndExcluding": "6.18.54" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.0", "versionEndExcluding": "7.2.8" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.0", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/2359264f377cdbdef2d95868cc8fb572949e48d3" }, { "url": "https://git.kernel.org/stable/c/69a768c12398cada8528080332c822623fa7064d" }, { "url": "https://git.kernel.org/stable/c/6508304ac2c8cdafca2f4ab915df8c707893e134" }, { "url": "https://git.kernel.org/stable/c/6cab554f2c0f28773f712ed3a5479103f42ce844" }, { "url": "https://git.kernel.org/stable/c/0d0845ee61c5df47cc68bc446501f48f71e8dcc6" }, { "url": "https://git.kernel.org/stable/c/f89416eb3db151170a6f3c6dfc5239d26cdce4d2" } ], "title": "esp: downgrade zerocopy managed frags before mutating skb frags", "x_generator": { "engine": "bippy-1.2.0" } } } }