{"id":"CVE-2026-98548","title":"sctp: discard the rest of the packet on a stale-cookie error","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nsctp: discard the rest of the packet on a stale-cookie error\n\nWhen an association is in COOKIE-ECHOED state and the peer sends a\nbundled [ERROR(Stale Cookie)][DATA] pac…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < c0af3fd150fdc43821df3bb77e5ec74faf4dfc7a","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 854c053c71459f8db7ef07db9cfa4eec5f5206f2","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 965e21ea16acb394d5e5801998ca9b0adc669665","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 1cd246b214dc9acf4e2f11d58c035e1e672fe7d2","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < d68c9287b3ca0d6faadc61fbcb18d1a6b5493321","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < ec23855274a73906b02f0d124fefd9cb3c008b1d","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 6df536c5acbc0abd6f119d02e24f4a2ed97707f4","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 4498467a8af06cfa3d71cb04bd7c4170dec8f449","Linux 2.6.12"],"published":"2026-10-18","updated":"2026-10-18","sourceUpdated":"2026-10-18T15:18:16.510Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98548","references":[{"url":"https://git.kernel.org/stable/c/c0af3fd150fdc43821df3bb77e5ec74faf4dfc7a"},{"url":"https://git.kernel.org/stable/c/854c053c71459f8db7ef07db9cfa4eec5f5206f2"},{"url":"https://git.kernel.org/stable/c/965e21ea16acb394d5e5801998ca9b0adc669665"},{"url":"https://git.kernel.org/stable/c/1cd246b214dc9acf4e2f11d58c035e1e672fe7d2"},{"url":"https://git.kernel.org/stable/c/d68c9287b3ca0d6faadc61fbcb18d1a6b5493321"},{"url":"https://git.kernel.org/stable/c/ec23855274a73906b02f0d124fefd9cb3c008b1d"},{"url":"https://git.kernel.org/stable/c/6df536c5acbc0abd6f119d02e24f4a2ed97707f4"},{"url":"https://git.kernel.org/stable/c/4498467a8af06cfa3d71cb04bd7c4170dec8f449"}],"tags":["cve.org"],"ingestedAt":"2026-10-18T15:45:12.265Z","slug":"CVE-2026-98548","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nsctp: discard the rest of the packet on a stale-cookie error\n\nWhen an association is in COOKIE-ECHOED state and the peer sends a\nbundled [ERROR(Stale Cookie)][DATA] packet from one of its non-primary\naddresses, processing the ERROR chunk takes the non-fatal stale-cookie\nretry path sctp_sf_do_5_2_6_stale(), which queues\nSCTP_CMD_DEL_NON_PRIMARY while keeping the association alive.\nsctp_cmd_del_non_primary() removes every non-primary transport -\nincluding the very transport this packet arrived on, which is still\nreferenced by the receive lookup and shared by all chunks of the\npacket via chunk->transport.\n\nsctp_assoc_rm_peer() does redirect asoc->peer.last_data_from away from\nthe removed transport, but right afterwards the bundled DATA chunk\nmakes sctp_assoc_bh_rcv() re-register\nasoc->peer.last_data_from = chunk->transport unconditionally, undoing\nthe redirection with the just-removed transport.\n\nOnce the packet is done, the receive reference is dropped and the\ntransport is RCU-freed, while the surviving association keeps the\ndangling last_data_from.  A later FWD-TSN (or the delayed SACK timer)\nmakes sctp_gen_sack() dereference it (->param_flags and friends), and\nsctp_make_sack()/sctp_outq_select_transport() may write to the freed\nobject and link it into the live transport list.  This is a\nuse-after-free triggerable by any malicious SCTP peer (or a local\nunprivileged user acting as one) with no capabilities required:\n\n  BUG: KASAN: slab-use-after-free in sctp_do_sm+0x498a/0x5660\n  Read of size 4 at addr ffff88800e1e356c by task poc/115\n  Call Trace: sctp_do_sm <- sctp_assoc_bh_rcv <- sctp_inq_push <-\n              sctp_rcv <- ip_protocol_deliver_rcu <- ip_rcv\n  Allocated: sctp_transport_new <- sctp_assoc_add_peer <-\n             sctp_process_init (INIT-ACK processing)\n  Freed: kfree <- sctp_transport_destroy_rcu <- rcu_core\n         (call_rcu queued by sctp_transport_put at end of sctp_rcv)\n  The buggy address is located 364 bytes inside of freed 1024-byte\n  region [ffff88800e1e3400, ffff88800e1e3800), cache kmalloc-1k\n\nNote that commit 03a9d10ecf71 (\"sctp: drop a chunk if its transport\nwas removed\") only covers the window between the receive lookup and\nthe chunk processing (e.g. an ASCONF DEL-IP racing the socket backlog);\nhere the transport is removed *while* the packet is being processed,\nby an earlier chunk of the same packet, so the drop in sctp_inq_push()\ndoes not reach this path.  Verified with the bundled [ERROR(Stale\nCookie)][DATA] + FWD-TSN reproducer: the KASAN report above still\nfires with that commit applied, and is gone with this patch on top.\n\nFix it by discarding the rest of the packet on this path, as suggested\nby Xin.  After the stale-cookie ERROR has sent the association back to\nCOOKIE-WAIT and removed the non-primary transports, the remaining\nchunks of the packet can only run against the restarted handshake\nwhile referencing the removed arrival transport through\nchunk->transport: besides the last_data_from registration above,\nsctp_cmd_setup_t2() and the sctp_make_*() reply builders would also\ncopy that pointer into association-lifetime state that\nsctp_assoc_rm_peer() has already sanitized.  Let the peer retransmit\nthem, in line with what sctp_inq_push() does for chunks whose\ntransport was removed before processing.\n\n## Affected\n\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < c0af3fd150fdc43821df3bb77e5ec74faf4dfc7a`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 854c053c71459f8db7ef07db9cfa4eec5f5206f2`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 965e21ea16acb394d5e5801998ca9b0adc669665`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 1cd246b214dc9acf4e2f11d58c035e1e672fe7d2`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < d68c9287b3ca0d6faadc61fbcb18d1a6b5493321`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < ec23855274a73906b02f0d124fefd9cb3c008b1d`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 6df536c5acbc0abd6f119d02e24f4a2ed97707f4`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 4498467a8af06cfa3d71cb04bd7c4170dec8f449`\n- `Linux 2.6.12`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}