CVE-2026-98548 (GCVE-0-2026-98548)
Vulnerability from cvelistv5
Published
2026-10-18 15:18
Modified
2026-10-24 14:09
Severity ?
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: sctp: discard the rest of the packet on a stale-cookie error When an association is in COOKIE-ECHOED state and the peer sends a bundled [ERROR(Stale Cookie)][DATA] packet from one of its non-primary addresses, processing the ERROR chunk takes the non-fatal stale-cookie retry path sctp_sf_do_5_2_6_stale(), which queues SCTP_CMD_DEL_NON_PRIMARY while keeping the association alive. sctp_cmd_del_non_primary() removes every non-primary transport - including the very transport this packet arrived on, which is still referenced by the receive lookup and shared by all chunks of the packet via chunk->transport. sctp_assoc_rm_peer() does redirect asoc->peer.last_data_from away from the removed transport, but right afterwards the bundled DATA chunk makes sctp_assoc_bh_rcv() re-register asoc->peer.last_data_from = chunk->transport unconditionally, undoing the redirection with the just-removed transport. Once the packet is done, the receive reference is dropped and the transport is RCU-freed, while the surviving association keeps the dangling last_data_from. A later FWD-TSN (or the delayed SACK timer) makes sctp_gen_sack() dereference it (->param_flags and friends), and sctp_make_sack()/sctp_outq_select_transport() may write to the freed object and link it into the live transport list. This is a use-after-free triggerable by any malicious SCTP peer (or a local unprivileged user acting as one) with no capabilities required: BUG: KASAN: slab-use-after-free in sctp_do_sm+0x498a/0x5660 Read of size 4 at addr ffff88800e1e356c by task poc/115 Call Trace: sctp_do_sm <- sctp_assoc_bh_rcv <- sctp_inq_push <- sctp_rcv <- ip_protocol_deliver_rcu <- ip_rcv Allocated: sctp_transport_new <- sctp_assoc_add_peer <- sctp_process_init (INIT-ACK processing) Freed: kfree <- sctp_transport_destroy_rcu <- rcu_core (call_rcu queued by sctp_transport_put at end of sctp_rcv) The buggy address is located 364 bytes inside of freed 1024-byte region [ffff88800e1e3400, ffff88800e1e3800), cache kmalloc-1k Note that commit 03a9d10ecf71 ("sctp: drop a chunk if its transport was removed") only covers the window between the receive lookup and the chunk processing (e.g. an ASCONF DEL-IP racing the socket backlog); here the transport is removed *while* the packet is being processed, by an earlier chunk of the same packet, so the drop in sctp_inq_push() does not reach this path. Verified with the bundled [ERROR(Stale Cookie)][DATA] + FWD-TSN reproducer: the KASAN report above still fires with that commit applied, and is gone with this patch on top. Fix it by discarding the rest of the packet on this path, as suggested by Xin. After the stale-cookie ERROR has sent the association back to COOKIE-WAIT and removed the non-primary transports, the remaining chunks of the packet can only run against the restarted handshake while referencing the removed arrival transport through chunk->transport: besides the last_data_from registration above, sctp_cmd_setup_t2() and the sctp_make_*() reply builders would also copy that pointer into association-lifetime state that sctp_assoc_rm_peer() has already sanitized. Let the peer retransmit them, in line with what sctp_inq_push() does for chunks whose transport was removed before processing.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
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{
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              "negate": false,
              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "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] 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-\u003etransport.\n\nsctp_assoc_rm_peer() does redirect asoc-\u003epeer.last_data_from away from\nthe removed transport, but right afterwards the bundled DATA chunk\nmakes sctp_assoc_bh_rcv() re-register\nasoc-\u003epeer.last_data_from = chunk-\u003etransport 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 (-\u003eparam_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 \u003c- sctp_assoc_bh_rcv \u003c- sctp_inq_push \u003c-\n              sctp_rcv \u003c- ip_protocol_deliver_rcu \u003c- ip_rcv\n  Allocated: sctp_transport_new \u003c- sctp_assoc_add_peer \u003c-\n             sctp_process_init (INIT-ACK processing)\n  Freed: kfree \u003c- sctp_transport_destroy_rcu \u003c- 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-\u003etransport: 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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - ip_protocol_deliver_rcu() invokes sctp4_rcv()/sctp6_rcv(), then sctp_rcv()-\u003esctp_inq_push()-\u003esctp_assoc_bh_rcv()-\u003esctp_do_sm(); a routable peer supplies the bundled SCTP ERROR(Stale Cookie)+DATA that reaches patched sctp_sf_do_5_2_6_stale().\nAC:L - The peer controls every step: its INIT-ACK advertises a secondary address, it sends ERROR+DATA from that address, completes the restarted handshake, waits for RCU reclamation, and sends FWD-TSN; no race or external state is required.\nPR:N - sctp_sf_cookie_echoed_err() checks only sctp_vtag_verify(); the peer learns asoc-\u003ec.my_vtag from the victim\u0027s INIT, and ERROR is absent from the default SCTP-AUTH-required chunk list, so no credentials or capabilities are required.\nUI:N - Once the target\u0027s SCTP client starts its ordinary association, sctp_rcv() processes the peer\u0027s ERROR+DATA, retry-handshake, and FWD-TSN packets automatically; an autonomous client or reconnector requires no human action.\nS:U - The dangling sctp_transport is consumed by sctp_gen_sack() and sctp_outq_select_transport() within the same host-kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - sctp_assoc_bh_rcv() stores the removed transport in last_data_from; after sctp_transport_destroy_rcu() frees that kmalloc-1k object, sctp_gen_sack() reads attacker-reclaimable param_flags, sackfreq, and sackdelay, creating an exploitable UAF capable of kernel-memory disclosure.\nI:H - sctp_make_sack() copies the dangling pointer into its reply, and sctp_outq_select_transport() treats the reclaimed object as live, writing send_ready links via list_add_tail() and modifying packet, cwnd, and burst_limited fields, enabling exploitable kernel heap corruption.\nA:H - A later attacker-sent FWD-TSN reaches sctp_sf_eat_fwd_tsn()-\u003eSCTP_CMD_GEN_SACK; sctp_gen_sack() then dereferences the freed transport and can oops or panic, as demonstrated by the reproduced KASAN slab-use-after-free."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-24T14:09:21.243Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "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"
        }
      ],
      "title": "sctp: discard the rest of the packet on a stale-cookie error",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98548",
    "datePublished": "2026-10-18T15:18:16.510Z",
    "dateReserved": "2026-09-25T10:25:14.356Z",
    "dateUpdated": "2026-10-24T14:09:21.243Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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