{"id":"DEBIAN-CVE-2026-64450","details":"In the Linux kernel, the following vulnerability has been resolved:  tipc: fix out-of-bounds read in broadcast Gap ACK blocks  A broadcast PROTOCOL/STATE_MSG can carry a Gap ACK blocks record in its data area. tipc_get_gap_ack_blks() only verifies that the record's len field is self-consistent with its ugack_cnt/bgack_cnt counts (sz == struct_size(p, gacks, ugack_cnt + bgack_cnt)); it does not check that the record actually fits in the message data area, msg_data_sz().  The unicast caller tipc_link_proto_rcv() bounds it (\"if (glen \u003e dlen) break;\"), but the broadcast caller tipc_bcast_sync_rcv() discards the returned size, so tipc_link_advance_transmq() copies the record off the receive skb with an attacker-controlled count:  \tthis_ga = kmemdup(ga, struct_size(ga, gacks, ga-\u003ebgack_cnt), \t\t\t  GFP_ATOMIC);  A TIPC neighbour that negotiated TIPC_GAP_ACK_BLOCK triggers it with one ordinary broadcast STATE_MSG (msg_bc_ack_invalid() clear), sized so its data area is short, carrying a Gap ACK record with len = 0x400, bgack_cnt = 0xff and ugack_cnt = 0. len then equals struct_size(p, gacks, 255), so the consistency check passes and ga is non-NULL; kmemdup() reads struct_size(ga, gacks, 255) = 1024 bytes out of the much smaller skb:    BUG: KASAN: slab-out-of-bounds in kmemdup_noprof+0x48/0x60   Read of size 1024 at addr ffff0000c7030d38 by task poc864/69   Call trace:    kmemdup_noprof+0x48/0x60    tipc_link_advance_transmq+0x86c/0xb80    tipc_link_bc_ack_rcv+0x19c/0x1e0    tipc_bcast_sync_rcv+0x1c4/0x2c4    tipc_rcv+0x85c/0x1340    tipc_l2_rcv_msg+0xac/0x104   The buggy address belongs to the object at ffff0000c7030d00    which belongs to the cache skbuff_small_head of size 704   The buggy address is located 56 bytes inside of    allocated 704-byte region [ffff0000c7030d00, ffff0000c7030fc0)  The copied-out bytes are subsequently consumed as gap/ack values, but the read is already out of bounds at the kmemdup() regardless of how they are used.  The unicast STATE path drops such a message: \"if (glen \u003e dlen) break;\" skips the rest of STATE_MSG handling and the skb is freed. Make the broadcast path drop it too. tipc_bcast_sync_rcv() now bounds the record against msg_data_sz() and, when it does not fit, reports it back through tipc_node_bc_sync_rcv() to tipc_rcv() so the skb is discarded rather than processed. ga is not cleared on this path: ga == NULL already means \"legacy peer without Selective ACK\", a distinct legitimate state.","modified":"2026-09-14T17:03:48.869484537Z","published":"2026-07-25T10:17:29.850Z","upstream":["CVE-2026-64450"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-64450"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.180-1"}]}],"versions":["6.1.106-1","6.1.106-2","6.1.106-3","6.1.112-1","6.1.115-1","6.1.119-1","6.1.123-1","6.1.124-1","6.1.128-1","6.1.129-1","6.1.133-1","6.1.135-1","6.1.137-1","6.1.139-1","6.1.140-1","6.1.147-1","6.1.148-1","6.1.153-1","6.1.158-1","6.1.159-1","6.1.162-1","6.1.164-1","6.1.170-1","6.1.170-2","6.1.170-3","6.1.172-1","6.1.174-1","6.1.176-1","6.1.177-1","6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1","6.1.99-1"],"ecosystem_specific":{"urgency":"not 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