{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2023-53635", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-10-07T15:16:59.657Z", "datePublished": "2025-10-07T15:19:36.973Z", "dateUpdated": "2026-08-05T09:15:15.798Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T09:15:15.798Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: conntrack: fix wrong ct->timeout value\n\n(struct nf_conn)->timeout is an interval before the conntrack\nconfirmed. After confirmed, it becomes a timestamp.\n\nIt is observed that timeout of an unconfirmed conntrack:\n- Set by calling ctnetlink_change_timeout(). As a result,\n `nfct_time_stamp` was wrongly added to `ct->timeout` twice.\n- Get by calling ctnetlink_dump_timeout(). As a result,\n `nfct_time_stamp` was wrongly subtracted.\n\nCall Trace:\n \n dump_stack_lvl\n ctnetlink_dump_timeout\n __ctnetlink_glue_build\n ctnetlink_glue_build\n __nfqnl_enqueue_packet\n nf_queue\n nf_hook_slow\n ip_mc_output\n ? __pfx_ip_finish_output\n ip_send_skb\n ? __pfx_dst_output\n udp_send_skb\n udp_sendmsg\n ? __pfx_ip_generic_getfrag\n sock_sendmsg\n\nSeparate the 2 cases in:\n- Setting `ct->timeout` in __nf_ct_set_timeout().\n- Getting `ct->timeout` in ctnetlink_dump_timeout().\n\nPablo appends:\n\nUpdate ctnetlink to set up the timeout _after_ the IPS_CONFIRMED flag is\nset on, otherwise conntrack creation via ctnetlink breaks.\n\nNote that the problem described in this patch occurs since the\nintroduction of the nfnetlink_queue conntrack support, select a\nsufficiently old Fixes: tag for -stable kernel to pick up this fix." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H", "baseScore": 8.2, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - The corruption occurs in the conntrack packet path — every new flow traversing an NFQUEUE-with-conntrack ruleset (IPS/firewall daemons) or a tc/XDP conntrack BPF program gets its `ct->timeout` mangled during `nf_hook_slow`/`nf_confirm` processing of received packets. A remote peer sending traffic to such a host drives the enqueue/verdict/confirm cycle and controls the rate at which broken entries accumulate.\nAC:L - The double-add of `nfct_time_stamp` is deterministic for every unconfirmed conntrack whose timeout is set, with no race, memory-layout, or timing dependency; the attacker simply generates new flows. Scoring the vulnerable (queue/BPF conntrack-enabled) deployment, no condition lies outside the attacker's control.\nPR:N - On a host running a conntrack-aware NFQUEUE daemon or BPF conntrack program, unauthenticated remote packets are sufficient to create the mis-timed entries — no credentials on the target are needed. Even in the purely local framing, the nfnetlink gate is `netlink_net_capable(CAP_NET_ADMIN)`, which is namespace-scoped and reachable by an unprivileged user via `unshare -Urn`.\nUI:N - Exploitation is entirely driven by network traffic and the kernel's own enqueue/verdict/confirm cycle; no victim action of any kind is required.\nS:U - The corrupted state (`ct->timeout`) and its effects stay within the kernel networking subsystem's own security authority. No VM, IOMMU, or sandbox boundary is crossed.\nC:N - No kernel memory is read out of bounds and no sensitive data is exposed; the only wrong value returned is a bogus timeout in `ctnetlink_dump_timeout()`, delivered to an already-privileged queue daemon and derived from `jiffies`, which is not sensitive.\nI:L - The bug writes an incorrect lifetime into kernel-managed connection-tracking state, so tracked flows either persist far past their policy-mandated expiry (keeping stateful `ESTABLISHED` acceptance and NAT bindings alive) or vanish immediately, altering the firewall policy the kernel enforces. The modification is limited and its resulting value is not attacker-chosen.\nA:H - Entries that never age out fill the conntrack table, after which the host drops all new connections (`nf_conntrack: table full`) and the condition persists for days rather than the configured 30–120 s; in the opposite regime every new entry is expired at confirmation, breaking stateful filtering and NAT for all traffic. Either outcome is a complete loss of the host's networking availability." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/net/netfilter/nf_conntrack_core.h", "net/netfilter/nf_conntrack_netlink.c" ], "versions": [ { "version": "a4b4766c3cebb4018167e06b863d8e95b7274757", "lessThan": "80c5ba0078e20d926d11d0778f9a43902664ebf0", "status": "affected", "versionType": "git" }, { "version": "a4b4766c3cebb4018167e06b863d8e95b7274757", "lessThan": "ff5e4ac8dd7be7f1faba955c5779a68571eeb0f8", "status": "affected", "versionType": "git" }, { "version": "a4b4766c3cebb4018167e06b863d8e95b7274757", "lessThan": "f612ae1ab4793701caf39386fb3b7f4b3ef44e48", "status": "affected", "versionType": "git" }, { "version": "a4b4766c3cebb4018167e06b863d8e95b7274757", "lessThan": "73db1b8f2bb6725b7391e85aab41fdf592b3c0c1", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/net/netfilter/nf_conntrack_core.h", "net/netfilter/nf_conntrack_netlink.c" ], "versions": [ { "version": "4.4", "status": "affected" }, { "version": "0", "lessThan": "4.4", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.28", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.2.15", "lessThanOrEqual": "6.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.3.2", "lessThanOrEqual": "6.3.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.4", "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": "4.4", "versionEndExcluding": "6.1.28" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "6.2.15" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "6.3.2" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "6.4" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/80c5ba0078e20d926d11d0778f9a43902664ebf0" }, { "url": "https://git.kernel.org/stable/c/ff5e4ac8dd7be7f1faba955c5779a68571eeb0f8" }, { "url": "https://git.kernel.org/stable/c/f612ae1ab4793701caf39386fb3b7f4b3ef44e48" }, { "url": "https://git.kernel.org/stable/c/73db1b8f2bb6725b7391e85aab41fdf592b3c0c1" } ], "title": "netfilter: conntrack: fix wrong ct->timeout value", "x_generator": { "engine": "bippy-1.2.0" } } } }