{"id":"CVE-2026-98104","revision":"43c277980e1f48db9dcdd0ce1160af94","records":[{"revision":"43c277980e1f48db9dcdd0ce1160af94","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-98104","aliases":[],"title":"net/sched: cls_u32: fix duplicate handle when node ID pool is exhausted","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_u32: fix duplicate handle when node ID pool is exhausted\n\ngen_new_kid() falls back to returning max (htid | 0xFFF) when both\nidr_alloc_u32() ranges are full, instead of reporting an error.\nu32_change() trusts that value and inserts a new knode with a handle\nthat is already live in the hash table, breaking handle uniqueness\nwithin the table's node ID space.\n\nThe handle was never reserved in ht->handle_idr, so every later error\npath that does idr_remove(&ht->handle_idr, handle) removes the\nreservation of a different, live knode, which is then reused — one\nfailed add compounds into further duplicates.\n\nThe 4095 limit is per (table, bucket) — ht->handle_idr is per hash\ntable and the range is derived from htid (bucketid), so a table with\ndivisor 256 can legitimately hold 256*4095 knodes.\n\nThe sibling helper gen_new_htid() has the same silent in-band failure:\nit returns 0 when the tp_c handle pool (1..0x7FF) is full, and\nu32_init() publishes the root hash table with handle 0 without\nchecking. Two root tables with handle 0 alias in u32_lookup_ht(),\nallowing cross-tcf_proto knode add/lookup/delete. Add the same\nexhaustion check that the divisor path already has.\n\nReturn an error so u32_change() fails with ENOSPC/ENOMEM when the\nnode ID space is exhausted, and so u32_init() fails with -ENOMEM\nwhen the hash table ID space is exhausted. The extack message\ndistinguishes pool exhaustion (-ENOSPC) from a transient allocation\nfailure (-ENOMEM).\n\nConditions to recreate the bug:\n- CONFIG_NET_SCHED=y, CONFIG_CLS_U32=y (or =m with module loaded)\n- Create a clsact qdisc on a device, then add 4095 u32 filters with\n auto-generated handles to fill the node ID space for the root hash\n table (single bucket). The 4096th auto-handle filter add triggers\n the duplicate handle (fh 800::fff reused). Reachable at Level 2\n (unshare -Urn, namespace-local CAP_NET_ADMIN).\n- For gen_new_htid: create 2047 u32 proto entries on the same block\n to fill the tp_c handle pool, then create one more. The root table\n gets handle 0 and aliases with other handle-0 root tables.","state":0,"publishedAt":"2026-09-25T10:35:54.544+00:00","modifiedAt":"2026-10-19T09:13:56.808+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"unaffected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"net/sched/cls_u32.c\"\n ],\n \"versions\": [\n {\n \"version\": \"7801db8aec957fa6610efe0ee26a6c8bc0f1d73b\",\n \"lessThan\": \"f4ee13ed7f7b22dcd8287fcf477ae37bd84567da\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"7801db8aec957fa6610efe0ee26a6c8bc0f1d73b\",\n \"lessThan\": \"84223baf21bc9b008444ae9bc38d5fb91fe00b9d\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"7801db8aec957fa6610efe0ee26a6c8bc0f1d73b\",\n \"lessThan\": \"6890e28840bae4f6805e8de981c4ec8e12a4e064\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"7801db8aec957fa6610efe0ee26a6c8bc0f1d73b\",\n \"lessThan\": \"feab9261b537df4ebb8350e4779bc185373059fd\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"7801db8aec957fa6610efe0ee26a6c8bc0f1d73b\",\n \"lessThan\": \"f594f04268d01c5fdc975f3f51fc219ea2159ac6\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"7801db8aec957fa6610efe0ee26a6c8bc0f1d73b\",\n \"lessThan\": \"d7e7e98d23f42a92d9ab7e36302bd96bd9b33b5f\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n }\n ]\n }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"affected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"net/sched/cls_u32.c\"\n ],\n \"versions\": [\n {\n \"version\": \"3.16\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"3.16\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.1.189\",\n \"lessThanOrEqual\": \"6.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.158\",\n \"lessThanOrEqual\": \"6.6.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.111\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18.53\",\n \"lessThanOrEqual\": \"6.18.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.2.7\",\n \"lessThanOrEqual\": \"7.2.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.3\",\n \"lessThanOrEqual\": \"*\",\n \"status\": \"unaffected\",\n \"versionType\": \"original_commit_for_fix\"\n }\n ]\n }"}],"metrics":[],"references":["https://git.kernel.org/stable/c/f4ee13ed7f7b22dcd8287fcf477ae37bd84567da","https://git.kernel.org/stable/c/84223baf21bc9b008444ae9bc38d5fb91fe00b9d","https://git.kernel.org/stable/c/6890e28840bae4f6805e8de981c4ec8e12a4e064","https://git.kernel.org/stable/c/feab9261b537df4ebb8350e4779bc185373059fd","https://git.kernel.org/stable/c/f594f04268d01c5fdc975f3f51fc219ea2159ac6","https://git.kernel.org/stable/c/d7e7e98d23f42a92d9ab7e36302bd96bd9b33b5f"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98104","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-98104","identifiers":["CVE-2026-98104"]},"retained":false,"historicalAffected":[]}],"coverage":[]}