{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-93105", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-17T16:02:15.085Z", "datePublished": "2026-09-17T16:11:16.442Z", "dateUpdated": "2026-10-19T09:05:38.089Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T09:05:38.089Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nesp: do not unref managed frag pages in esp_ssg_unref()\n\nesp_ssg_unref() releases the page references held on the source\nscatterlist after the AEAD operation completes. It calls\nskb_page_unref() on every frag page for an out-of-place transform\n(req->src != req->dst), and in the error path of esp_output_tail()\n(already_unref == true) on the request's own scatterlist.\n\nThis is wrong when the skb carries managed frags\n(SKBFL_MANAGED_FRAG_REFS). Managed frags are owned by a zerocopy ubuf\nand the skb does not hold a per-frag page reference; io_uring SEND_ZC\nwith a registered buffer attaches the bvec pages this way via\nio_sg_from_iter(). The rest of the stack honours this invariant:\nskb_release_data() skips the per-frag unref when SKBFL_MANAGED_FRAG_REFS\nis set, and skb_zcopy_managed() is the guard used at the other unref\nsites.\n\nesp_ssg_unref() is missing that guard, so for a managed-frag skb it\ndrops a page reference the skb never acquired. This can underflow the\npage reference count and free a page that is still in use.\n\nGuard the function with skb_zcopy_managed() so both unref paths are\nskipped for managed-frag skbs, matching skb_release_data()." } ], "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 extra unref is reached from IORING_OP_SEND_ZC/SENDMSG_ZC with IORING_RECVSEND_FIXED_BUF: io_sendmsg_zc() -> sock_sendmsg() -> tcp_sendmsg_locked() -> xfrm_output() -> esp_output_tail() -> esp_ssg_unref(). io_sg_from_iter() is the only site that sets SKBFL_MANAGED_FRAG_REFS; esp_input() never calls esp_ssg_unref(), so a remote ESP packet cannot supply the buggy skb.\nAC:L - tcp_stream_alloc_skb() allocates MAX_TCP_HEADER then skb_reserve()s all of it, so a SEND_ZC TCP skb has ~0 tailroom. esp_output_head() therefore takes inplace=false (tailen > tailroom, nr_frags < MAX_SKB_FRAGS, data_len+tailen <= PAGE_SIZE), after which esp_output_tail() replaces the frags and esp_ssg_unref() always drops the managed pages. The attacker chooses the send size.\nPR:L - io_uring_setup() allows IORING_OP_SEND_ZC when sysctl_io_uring_disabled==0 (default); no capability is checked on that send path. An ESP SA is also required: the attacker can add one in a user+net namespace because xfrm_user_rcv_msg() only tests netlink_net_capable(CAP_NET_ADMIN) against the netns user_ns, or can send through an already-installed IPsec policy.\nUI:N - The attacker registers the buffer with IORING_REGISTER_BUFFERS, submits SEND_ZC, and if needed installs the XFRM state/policy; no other user must open a file, mount a volume, or otherwise act.\nS:U - esp_ssg_unref()'s extra put_page() corrupts host kernel page refcounts. That is a conventional local privilege escalation inside the same kernel, not a KVM/Xen guest-to-host or IOMMU-scope change.\nC:H - After the out-of-place transform, esp_ssg_unref() calls skb_page_unref() on every source sg page past skb->data. Those pages were attached by io_sg_from_iter() without a per-frag get_page(), so the extra put underflows the refcount of still-mapped IORING_REGISTER_BUFFERS pages and frees memory the attacker can read.\nI:H - The same extra skb_page_unref() frees registered-buffer pages that remain in the io_uring bvec and the attacker's userspace mapping, so the page can be reallocated and overwritten, giving an arbitrary write and control-flow hijack.\nA:H - The extra put_page() on managed frag pages underflows the page refcount and frees a page still in use, which oopses with bad page state even when the use-after-free is not turned into a full memory-corruption exploit." } ] } ], "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": "cac2661c53f35cbe651bef9b07026a5a05ab8ce0", "lessThan": "1ad6456898f6e6cf58be83bdb607acb1119a9cd1", "status": "affected", "versionType": "git" }, { "version": "cac2661c53f35cbe651bef9b07026a5a05ab8ce0", "lessThan": "26b6b14c7a0368e317a1e9fb5144ebe6f8d495cf", "status": "affected", "versionType": "git" }, { "version": "cac2661c53f35cbe651bef9b07026a5a05ab8ce0", "lessThan": "21697720ff43b8dfa25b8e8d9ca7f56f4597fc80", "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": "4.11", "status": "affected" }, { "version": "0", "lessThan": "4.11", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.57", "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": "4.11", "versionEndExcluding": "6.18.57" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.11", "versionEndExcluding": "7.2.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.11", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/1ad6456898f6e6cf58be83bdb607acb1119a9cd1" }, { "url": "https://git.kernel.org/stable/c/26b6b14c7a0368e317a1e9fb5144ebe6f8d495cf" }, { "url": "https://git.kernel.org/stable/c/21697720ff43b8dfa25b8e8d9ca7f56f4597fc80" } ], "title": "esp: do not unref managed frag pages in esp_ssg_unref()", "x_generator": { "engine": "bippy-1.2.0" } } } }