{"cve":"CVE-2026-98122","nvd":{"published":"2026-09-25T11:17:43.470","modified":"2026-10-22T17:19:22.093","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nvxlan: mdb: Fix use-after-free in vxlan_mdb_remote_src_del()\n\nvxlan_mdb_is_valid_source(), which validates MDBE_ATTR_SOURCE and every\nMDBE_ATTR_SRC_LIST member, accepts the all-zeros address.\n\nA source list is only accepted on a (*, G) entry, whose source is the\nall-zeros address, and for each member of the list an (S, G) entry is\nderived from it by substituting the source. Entries are keyed by a plain\nmemcmp() of struct vxlan_mdb_entry_key, so if MDBE_ATTR_SOURCE is present\nand holds the all-zeros address and the source list holds it as well, the\nderived (S, G) key is byte-identical to the (*, G) key and resolves to the\nsame entry. Omitting MDBE_ATTR_SOURCE is not equivalent, as the key is\nthen left with a zero address family.\n\nvxlan_mdb_remote_src_del() removes the forwarding entry of a source before\nfreeing the source entry:\n\n\tvxlan_mdb_remote_src_fwd_del(vxlan, group, remote, &ent->addr);\n\tvxlan_mdb_remote_src_entry_del(ent);\n\nWith the keys aliased, the first call deletes the remote of the entry that\nowns 'ent' instead of a separate (S, G) entry, and frees 'ent'. The second\ncall then runs on the freed entry, and its hlist_del() reads ->pprev and\n->next out of it and writes through them.\n\nAdding the (*, G) entry with NLM_F_REPLACE and no source list marks the\nall-zeros source for deletion and reaches this from the sweep at the end\nof vxlan_mdb_remote_srcs_replace().\n\n  BUG: KASAN: slab-use-after-free in __vxlan_mdb_add+0x1cd/0xd70\n  Read of size 8 at addr ffff888102852500 by task poc/84\n   __vxlan_mdb_add+0x1cd/0xd70\n   vxlan_mdb_add+0xc0/0x140\n   rtnl_mdb_add+0x157/0x2a0\n   rtnetlink_rcv_msg+0x207/0x5a0\n  Allocated by task 84:\n   __kmalloc_cache_noprof+0x153/0x360\n   vxlan_mdb_remote_srcs_add+0x2eb/0x440\n   __vxlan_mdb_add+0x803/0xd70\n  Freed by task 84:\n   kfree+0x14c/0x3b0\n   vxlan_mdb_remote_del+0x129/0x1a0\n   __vxlan_mdb_del+0x4f/0xe0\n   vxlan_mdb_remote_src_fwd_del.isra.0+0x162/0x1b0\n   __vxlan_mdb_add+0x1c5/0xd70\n\nThe MDB operations are netns-scoped, so an unprivileged user can perform\nthem in a new user and network namespace.\n\nReject the all-zeros address in vxlan_mdb_is_valid_source(), which covers\nboth call sites. A (*, G) entry is expressed by omitting the source, so\nnothing legitimate is refused.\n\nDiscovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":["CWE-416"],"references":["https://git.kernel.org/stable/c/069d5527bb0f229e528fa88c6b72f15060c373f2","https://git.kernel.org/stable/c/4aa61c88b4e292e10abdfd791334b8272108d68a","https://git.kernel.org/stable/c/71203a41d6fa2fa0ea2f3a7541987958bd3694fd","https://git.kernel.org/stable/c/74e2a56c82209b0335b53e25f19f9b0590e2483d","https://git.kernel.org/stable/c/e12c903fd13c6261b98ca18d8f70ac26e739e2f8"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-23T16:39:26.291718493+00:00"},"epss":{"cve":"CVE-2026-98122","score":0.00125,"percentile":0.02189,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}