{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2025-21958", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-12-29T08:45:45.791Z", "datePublished": "2025-04-01T15:46:57.268Z", "dateUpdated": "2026-08-05T11:55:36.868Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T11:55:36.868Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nRevert \"openvswitch: switch to per-action label counting in conntrack\"\n\nCurrently, ovs_ct_set_labels() is only called for confirmed conntrack\nentries (ct) within ovs_ct_commit(). However, if the conntrack entry\ndoes not have the labels_ext extension, attempting to allocate it in\novs_ct_get_conn_labels() for a confirmed entry triggers a warning in\nnf_ct_ext_add():\n\n WARN_ON(nf_ct_is_confirmed(ct));\n\nThis happens when the conntrack entry is created externally before OVS\nincrements net->ct.labels_used. The issue has become more likely since\ncommit fcb1aa5163b1 (\"openvswitch: switch to per-action label counting\nin conntrack\"), which changed to use per-action label counting and\nincrement net->ct.labels_used when a flow with ct action is added.\n\nSince there’s no straightforward way to fully resolve this issue at the\nmoment, this reverts the commit to avoid breaking existing use cases." } ], "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 - Triggering requires installing an OVS datapath flow carrying a ct action with a non-zero label mask via the openvswitch generic-netlink interface, which is a local operation. Although the packet that fires the bug can arrive from the wire on an OVS/OVN host, the necessary local netlink configuration step makes Local the defensible vector.\nAC:L - The attacker fully controls the ordering that creates the bug — create the conntrack entry while net->ct.labels_used is zero, then install the ct-label flow, then re-send a packet of that connection — and equally controls the concurrent traffic that turns the krealloc of a hash-visible ct->ext into a use-after-free. No condition lies outside attacker influence.\nPR:L - All OVS datapath/flow/vport netlink commands use GENL_UNS_ADMIN_PERM, i.e. CAP_NET_ADMIN in the netns owner user namespace, which any unprivileged user obtains with unshare -Urn; nftables in the same namespace supplies the externally created conntrack entry.\nUI:N - The attacker performs every step — namespace setup, flow installation and packet injection — with no action from any other user.\nS:U - The corruption is confined to kernel heap objects belonging to the same kernel security authority; no VM, IOMMU or sandbox boundary is crossed.\nC:H - nf_ct_ext_add() reallocates ct->ext on a confirmed, hash-table-visible conntrack with no RCU grace period, so lock-free readers such as nf_conn_acct_find(), nfct_nat(), nf_ct_ecache_find() and nf_ct_labels_find() dereference freed memory, giving a use-after-free read that can be groomed to disclose arbitrary kernel heap contents.\nI:H - The same window is a use-after-free write — nf_ct_acct_update() performs atomic64_add() into the freed extension block, and nf_ct_ext_add() itself writes offsets and memsets into a buffer another CPU may already have reallocated — yielding heap corruption exploitable for control-flow hijack.\nA:H - The WARN_ON(nf_ct_is_confirmed(ct)) splat is an immediate kernel warning that panics the machine under panic_on_warn, and the underlying use-after-free readily causes oopses and slab corruption crashes." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/openvswitch/conntrack.c", "net/openvswitch/datapath.h" ], "versions": [ { "version": "fcb1aa5163b1ae4cf2864b688b08927aac51f51e", "lessThan": "9e79fdabd52cfce1a021640a81256878a2c516a2", "status": "affected", "versionType": "git" }, { "version": "fcb1aa5163b1ae4cf2864b688b08927aac51f51e", "lessThan": "d91bfc64a4886102746e74d2c6f3a61e9a77fd7d", "status": "affected", "versionType": "git" }, { "version": "fcb1aa5163b1ae4cf2864b688b08927aac51f51e", "lessThan": "1063ae07383c0ddc5bcce170260c143825846b03", "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/openvswitch/conntrack.c", "net/openvswitch/datapath.h" ], "versions": [ { "version": "6.12", "status": "affected" }, { "version": "0", "lessThan": "6.12", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.20", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.13.8", "lessThanOrEqual": "6.13.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.14", "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": "6.12", "versionEndExcluding": "6.12.20" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12", "versionEndExcluding": "6.13.8" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12", "versionEndExcluding": "6.14" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/9e79fdabd52cfce1a021640a81256878a2c516a2" }, { "url": "https://git.kernel.org/stable/c/d91bfc64a4886102746e74d2c6f3a61e9a77fd7d" }, { "url": "https://git.kernel.org/stable/c/1063ae07383c0ddc5bcce170260c143825846b03" } ], "title": "Revert \"openvswitch: switch to per-action label counting in conntrack\"", "x_generator": { "engine": "bippy-1.2.0" } } } }