{"id":"CVE-2026-64450","title":"tipc: fix out-of-bounds read in broadcast Gap ACK blocks","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\ntipc: fix out-of-bounds read in broadcast Gap ACK blocks\n\nA broadcast PROTOCOL/STATE_MSG can carry a Gap ACK blocks record in its\ndata area. tipc_get_gap_ack_blks() onl…","severity":"critical","cvss":9.1,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < 055663d21dc4336f67933ab26bef3c5934be6324","Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < 016f5995c37a5a2c45198308f830f244517d70b7","Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < 74b45af86a767594ba52330cd440ea84e24d700d","Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < 9a51115fcdc78687c8852bf93a1db3951dbb223b","Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < a21ed5064217cc33726da6c7ef1a520eba43aea1","Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < 2de42e268174766cb2e2b90721afdfdff70e0d8d","Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < f333b6851bdf326fd2134133272dbbed0c94d921","Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < 2b66974a1b6134a4bbc3bfed181f7418f688eb54","Linux 5.8"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-10-16T15:41:04.841993Z"},"published":"2026-07-25","updated":"2026-10-16","sourceUpdated":"2026-10-16T15:42:37.192Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-64450","references":[{"url":"https://git.kernel.org/stable/c/055663d21dc4336f67933ab26bef3c5934be6324"},{"url":"https://git.kernel.org/stable/c/016f5995c37a5a2c45198308f830f244517d70b7"},{"url":"https://git.kernel.org/stable/c/74b45af86a767594ba52330cd440ea84e24d700d"},{"url":"https://git.kernel.org/stable/c/9a51115fcdc78687c8852bf93a1db3951dbb223b"},{"url":"https://git.kernel.org/stable/c/a21ed5064217cc33726da6c7ef1a520eba43aea1"},{"url":"https://git.kernel.org/stable/c/2de42e268174766cb2e2b90721afdfdff70e0d8d"},{"url":"https://git.kernel.org/stable/c/f333b6851bdf326fd2134133272dbbed0c94d921"},{"url":"https://git.kernel.org/stable/c/2b66974a1b6134a4bbc3bfed181f7418f688eb54"}],"tags":["cve.org"],"epss":0.00537,"epssPercentile":0.44003,"ingestedAt":"2026-10-16T17:24:46.822Z","slug":"CVE-2026-64450","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\ntipc: fix out-of-bounds read in broadcast Gap ACK blocks\n\nA broadcast PROTOCOL/STATE_MSG can carry a Gap ACK blocks record in its\ndata area. tipc_get_gap_ack_blks() only verifies that the record's len\nfield is self-consistent with its ugack_cnt/bgack_cnt counts\n(sz == struct_size(p, gacks, ugack_cnt + bgack_cnt)); it does not check\nthat the record actually fits in the message data area, msg_data_sz().\n\nThe unicast caller tipc_link_proto_rcv() bounds it (\"if (glen > dlen)\nbreak;\"), but the broadcast caller tipc_bcast_sync_rcv() discards the\nreturned size, so tipc_link_advance_transmq() copies the record off the\nreceive skb with an attacker-controlled count:\n\n\tthis_ga = kmemdup(ga, struct_size(ga, gacks, ga->bgack_cnt),\n\t\t\t  GFP_ATOMIC);\n\nA TIPC neighbour that negotiated TIPC_GAP_ACK_BLOCK triggers it with one\nordinary broadcast STATE_MSG (msg_bc_ack_invalid() clear), sized so its\ndata area is short, carrying a Gap ACK record with len = 0x400,\nbgack_cnt = 0xff and ugack_cnt = 0. len then equals\nstruct_size(p, gacks, 255), so the consistency check passes and ga is\nnon-NULL; kmemdup() reads struct_size(ga, gacks, 255) = 1024 bytes out\nof the much smaller skb:\n\n  BUG: KASAN: slab-out-of-bounds in kmemdup_noprof+0x48/0x60\n  Read of size 1024 at addr ffff0000c7030d38 by task poc864/69\n  Call trace:\n   kmemdup_noprof+0x48/0x60\n   tipc_link_advance_transmq+0x86c/0xb80\n   tipc_link_bc_ack_rcv+0x19c/0x1e0\n   tipc_bcast_sync_rcv+0x1c4/0x2c4\n   tipc_rcv+0x85c/0x1340\n   tipc_l2_rcv_msg+0xac/0x104\n  The buggy address belongs to the object at ffff0000c7030d00\n   which belongs to the cache skbuff_small_head of size 704\n  The buggy address is located 56 bytes inside of\n   allocated 704-byte region [ffff0000c7030d00, ffff0000c7030fc0)\n\nThe copied-out bytes are subsequently consumed as gap/ack values, but\nthe read is already out of bounds at the kmemdup() regardless of how\nthey are used.\n\nThe unicast STATE path drops such a message: \"if (glen > dlen) break;\"\nskips the rest of STATE_MSG handling and the skb is freed. Make the\nbroadcast path drop it too. tipc_bcast_sync_rcv() now bounds the record\nagainst msg_data_sz() and, when it does not fit, reports it back through\ntipc_node_bc_sync_rcv() to tipc_rcv() so the skb is discarded rather than\nprocessed. ga is not cleared on this path: ga == NULL already means\n\"legacy peer without Selective ACK\", a distinct legitimate state.\n\n## Affected\n\n- `Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < 055663d21dc4336f67933ab26bef3c5934be6324`\n- `Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < 016f5995c37a5a2c45198308f830f244517d70b7`\n- `Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < 74b45af86a767594ba52330cd440ea84e24d700d`\n- `Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < 9a51115fcdc78687c8852bf93a1db3951dbb223b`\n- `Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < a21ed5064217cc33726da6c7ef1a520eba43aea1`\n- `Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < 2de42e268174766cb2e2b90721afdfdff70e0d8d`\n- `Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < f333b6851bdf326fd2134133272dbbed0c94d921`\n- `Linux >= d7626b5acff9227e2a65da636a53e09bdafdc0aa < 2b66974a1b6134a4bbc3bfed181f7418f688eb54`\n- `Linux 5.8`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":50,"depthScoreParts":{"impact":50.1,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}