{"id":"CVE-2024-26631","state":"PUBLISHED","title":"ipv6: mcast: fix data-race in ipv6_mc_down / mld_ifc_work","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: mcast: fix data-race in ipv6_mc_down / mld_ifc_work\n\nidev->mc_ifc_count can be written over without proper locking.\n\nOriginally found by syzbot [1], fix this issue by encapsulating calls\nto mld_ifc_stop_work() (and mld_gq_stop_work() for good measure) with\nmutex_lock() and mutex_unlock() accordingly as these functions\nshould only be called with mc_lock per their declarations.\n\n[1]\nBUG: KCSAN: data-race in ipv6_mc_down / mld_ifc_work\n\nwrite to 0xffff88813a80c832 of 1 bytes by task 3771 on cpu 0:\n mld_ifc_stop_work net/ipv6/mcast.c:1080 [inline]\n ipv6_mc_down+0x10a/0x280 net/ipv6/mcast.c:2725\n addrconf_ifdown+0xe32/0xf10 net/ipv6/addrconf.c:3949\n addrconf_notify+0x310/0x980\n notifier_call_chain kernel/notifier.c:93 [inline]\n raw_notifier_call_chain+0x6b/0x1c0 kernel/notifier.c:461\n __dev_notify_flags+0x205/0x3d0\n dev_change_flags+0xab/0xd0 net/core/dev.c:8685\n do_setlink+0x9f6/0x2430 net/core/rtnetlink.c:2916\n rtnl_group_changelink net/core/rtnetlink.c:3458 [inline]\n __rtnl_newlink net/core/rtnetlink.c:3717 [inline]\n rtnl_newlink+0xbb3/0x1670 net/core/rtnetlink.c:3754\n rtnetlink_rcv_msg+0x807/0x8c0 net/core/rtnetlink.c:6558\n netlink_rcv_skb+0x126/0x220 net/netlink/af_netlink.c:2545\n rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6576\n netlink_unicast_kernel net/netlink/af_netlink.c:1342 [inline]\n netlink_unicast+0x589/0x650 net/netlink/af_netlink.c:1368\n netlink_sendmsg+0x66e/0x770 net/netlink/af_netlink.c:1910\n ...\n\nwrite to 0xffff88813a80c832 of 1 bytes by task 22 on cpu 1:\n mld_ifc_work+0x54c/0x7b0 net/ipv6/mcast.c:2653\n process_one_work kernel/workqueue.c:2627 [inline]\n process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2700\n worker_thread+0x525/0x730 kernel/workqueue.c:2781\n ...","publishedAt":"2024-03-18T10:07:48.346Z","updatedAt":"2026-08-05T11:26:24.727Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"07a7a183f22cf1e3ce5ed336fe62a6248a2f6738","status":"affected","lessThan":"75ddcd741d2a30696f5893bc71a9d28f4ef22311","versionType":"git"},{"version":"2d9a93b4902be6a5504b5941dd15e9cd776aadca","status":"affected","lessThan":"62b3387beef11738eb6ce667601a28fa089fa02c","versionType":"git"},{"version":"2d9a93b4902be6a5504b5941dd15e9cd776aadca","status":"affected","lessThan":"380540bb06bb1d1b12bdc947d1b8f56cda6b5663","versionType":"git"},{"version":"2d9a93b4902be6a5504b5941dd15e9cd776aadca","status":"affected","lessThan":"3cc283fd16fba72e2cefe3a6f48d7a36b0438900","versionType":"git"},{"version":"2d9a93b4902be6a5504b5941dd15e9cd776aadca","status":"affected","lessThan":"3bb5849675ae1d592929798a2b37ea450879c855","versionType":"git"},{"version":"2d9a93b4902be6a5504b5941dd15e9cd776aadca","status":"affected","lessThan":"2e7ef287f07c74985f1bf2858bedc62bd9ebf155","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/mcast.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.13","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.13","versionType":"semver"},{"version":"5.15.148","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.75","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.14","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.7.2","status":"unaffected","lessThanOrEqual":"6.7.*","versionType":"semver"},{"version":"6.8","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/mcast.c"]}],"references":["https://git.kernel.org/stable/c/75ddcd741d2a30696f5893bc71a9d28f4ef22311","https://git.kernel.org/stable/c/62b3387beef11738eb6ce667601a28fa089fa02c","https://git.kernel.org/stable/c/380540bb06bb1d1b12bdc947d1b8f56cda6b5663","https://git.kernel.org/stable/c/3cc283fd16fba72e2cefe3a6f48d7a36b0438900","https://git.kernel.org/stable/c/3bb5849675ae1d592929798a2b37ea450879c855","https://git.kernel.org/stable/c/2e7ef287f07c74985f1bf2858bedc62bd9ebf155"],"weaknesses":[],"ingestedAt":"2026-10-29T20:07:10.607Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2024/26xxx/CVE-2024-26631.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2024-26631","state":"PUBLISHED","datePublished":"2024-03-18T10:07:48.346Z","dateUpdated":"2026-08-05T11:26:24.727Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2024-02-19T14:20:24.136Z"},"containers":{"cna":{"title":"ipv6: mcast: fix data-race in ipv6_mc_down / mld_ifc_work","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: mcast: fix data-race in ipv6_mc_down / mld_ifc_work\n\nidev->mc_ifc_count can be written over without proper locking.\n\nOriginally found by syzbot [1], fix this issue by encapsulating calls\nto mld_ifc_stop_work() (and mld_gq_stop_work() for good measure) with\nmutex_lock() and mutex_unlock() accordingly as these functions\nshould only be called with mc_lock per their declarations.\n\n[1]\nBUG: KCSAN: data-race in ipv6_mc_down / mld_ifc_work\n\nwrite to 0xffff88813a80c832 of 1 bytes by task 3771 on cpu 0:\n mld_ifc_stop_work net/ipv6/mcast.c:1080 [inline]\n ipv6_mc_down+0x10a/0x280 net/ipv6/mcast.c:2725\n addrconf_ifdown+0xe32/0xf10 net/ipv6/addrconf.c:3949\n addrconf_notify+0x310/0x980\n notifier_call_chain kernel/notifier.c:93 [inline]\n raw_notifier_call_chain+0x6b/0x1c0 kernel/notifier.c:461\n __dev_notify_flags+0x205/0x3d0\n dev_change_flags+0xab/0xd0 net/core/dev.c:8685\n do_setlink+0x9f6/0x2430 net/core/rtnetlink.c:2916\n rtnl_group_changelink net/core/rtnetlink.c:3458 [inline]\n __rtnl_newlink net/core/rtnetlink.c:3717 [inline]\n rtnl_newlink+0xbb3/0x1670 net/core/rtnetlink.c:3754\n rtnetlink_rcv_msg+0x807/0x8c0 net/core/rtnetlink.c:6558\n netlink_rcv_skb+0x126/0x220 net/netlink/af_netlink.c:2545\n rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6576\n netlink_unicast_kernel net/netlink/af_netlink.c:1342 [inline]\n netlink_unicast+0x589/0x650 net/netlink/af_netlink.c:1368\n netlink_sendmsg+0x66e/0x770 net/netlink/af_netlink.c:1910\n ...\n\nwrite to 0xffff88813a80c832 of 1 bytes by task 22 on cpu 1:\n mld_ifc_work+0x54c/0x7b0 net/ipv6/mcast.c:2653\n process_one_work kernel/workqueue.c:2627 [inline]\n process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2700\n worker_thread+0x525/0x730 kernel/workqueue.c:2781\n ..."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"07a7a183f22cf1e3ce5ed336fe62a6248a2f6738","status":"affected","lessThan":"75ddcd741d2a30696f5893bc71a9d28f4ef22311","versionType":"git"},{"version":"2d9a93b4902be6a5504b5941dd15e9cd776aadca","status":"affected","lessThan":"62b3387beef11738eb6ce667601a28fa089fa02c","versionType":"git"},{"version":"2d9a93b4902be6a5504b5941dd15e9cd776aadca","status":"affected","lessThan":"380540bb06bb1d1b12bdc947d1b8f56cda6b5663","versionType":"git"},{"version":"2d9a93b4902be6a5504b5941dd15e9cd776aadca","status":"affected","lessThan":"3cc283fd16fba72e2cefe3a6f48d7a36b0438900","versionType":"git"},{"version":"2d9a93b4902be6a5504b5941dd15e9cd776aadca","status":"affected","lessThan":"3bb5849675ae1d592929798a2b37ea450879c855","versionType":"git"},{"version":"2d9a93b4902be6a5504b5941dd15e9cd776aadca","status":"affected","lessThan":"2e7ef287f07c74985f1bf2858bedc62bd9ebf155","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/mcast.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.13","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.13","versionType":"semver"},{"version":"5.15.148","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.75","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.14","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.7.2","status":"unaffected","lessThanOrEqual":"6.7.*","versionType":"semver"},{"version":"6.8","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/mcast.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/75ddcd741d2a30696f5893bc71a9d28f4ef22311"},{"url":"https://git.kernel.org/stable/c/62b3387beef11738eb6ce667601a28fa089fa02c"},{"url":"https://git.kernel.org/stable/c/380540bb06bb1d1b12bdc947d1b8f56cda6b5663"},{"url":"https://git.kernel.org/stable/c/3cc283fd16fba72e2cefe3a6f48d7a36b0438900"},{"url":"https://git.kernel.org/stable/c/3bb5849675ae1d592929798a2b37ea450879c855"},{"url":"https://git.kernel.org/stable/c/2e7ef287f07c74985f1bf2858bedc62bd9ebf155"}],"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 `ipv6_mc_down()` side of the race is reached through local rtnetlink (`RTM_SETLINK`/`RTM_DELLINK` → `addrconf_notify`) and the opposing side through `setsockopt(IPV6_ADD_MEMBERSHIP)`, both local syscall interfaces. Although `mld_query_work` can additionally be fed by MLD query packets from a link-local peer, an adjacent attacker cannot initiate the interface-down half, so the self-contained attack is local.\nAC:L - The attacker drives both sides of the race deterministically and repeatedly: multicast join/leave and injected MLD queries queue `mc_ifc_work`/`mc_gq_work` while a concurrent thread loops `ip link set dev X down`, and `ipv6_mc_down()` uses non-sync `cancel_delayed_work()` for the query worker, guaranteeing an overlapping window on every iteration.\nPR:L - The rtnetlink gate is `netlink_net_capable(skb, CAP_NET_ADMIN)` → `netlink_ns_capable(..., sock_net(skb->sk)->user_ns, ...)`, which an unprivileged user obtains in a fresh netns via `unshare -Urn`; the multicast-join side requires no privilege at all.\nUI:N - The attacker performs every step — creating the device, joining groups, injecting MLD queries, and toggling the link down — with no victim action required.\nS:U - The corruption is confined to kernel IPv6 multicast state and the `inet6_dev` object within the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The unserialized `cancel_delayed_work()`/`in6_dev_hold()` window permits an `idev->refcnt` underflow through `__in6_dev_put()`'s unchecked `refcount_dec()`, leading to premature `kfree(idev)` while MLD workers still dereference it; a use-after-free on a kmalloc'd `inet6_dev` gives the attacker reads of resprayed heap contents.\nI:H - The same use-after-free is a write primitive: `struct inet6_dev` embeds five `delayed_work` structures whose `work->func` pointers the workqueue dispatches, plus `rs_timer` and `nd_parms`, so a resprayed object yields control-flow hijack; the race also corrupts adjacent packed fields (`mc_qrv`, `mc_gq_running`) that steer subsequent MLD state.\nA:H - The opposite interleaving orphans an `inet6_dev` reference so `in6_dev_finish_destroy()`/`netdev_put()` never run, wedging `unregister_netdevice: waiting for … to become free` permanently and blocking netns teardown under rtnl; the underflow direction produces `refcount_t` warnings and an oops."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T11:26:24.727Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"5.15.148"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"6.1.75"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"6.6.14"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"6.7.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"6.8"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CVE Program Container","references":[{"url":"https://git.kernel.org/stable/c/62b3387beef11738eb6ce667601a28fa089fa02c","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/380540bb06bb1d1b12bdc947d1b8f56cda6b5663","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/3cc283fd16fba72e2cefe3a6f48d7a36b0438900","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/3bb5849675ae1d592929798a2b37ea450879c855","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/2e7ef287f07c74985f1bf2858bedc62bd9ebf155","tags":["x_transferred"]}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2024-08-02T00:07:19.693Z"}},{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2024-08-27T14:55:41.665799Z","id":"CVE-2024-26631","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2024-08-27T14:55:52.147Z"}}]}}}