CVE-2026-98548
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.
Read full descriptionShow less
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:
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.
Technical details traces, logs and code from the original report
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-1kCVSS
NVD hasn't assigned a CVSS score to this CVE (common since the April 2026 policy change).
Exploitation probability (EPSS)
- Probability of exploitation in the next 30 days
- 0.21 %
- Percentile among all scored CVEs
- 11
- Score date
- 10/20/2026
EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).
Affected technologies (1)
⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.
References
Show 8 references
- https://git.kernel.org/stable/c/1cd246b214dc9acf4e2f11d58c035e1e672fe7d2
- https://git.kernel.org/stable/c/4498467a8af06cfa3d71cb04bd7c4170dec8f449
- https://git.kernel.org/stable/c/6df536c5acbc0abd6f119d02e24f4a2ed97707f4
- https://git.kernel.org/stable/c/854c053c71459f8db7ef07db9cfa4eec5f5206f2
- https://git.kernel.org/stable/c/965e21ea16acb394d5e5801998ca9b0adc669665
- https://git.kernel.org/stable/c/c0af3fd150fdc43821df3bb77e5ec74faf4dfc7a
- https://git.kernel.org/stable/c/d68c9287b3ca0d6faadc61fbcb18d1a6b5493321
- https://git.kernel.org/stable/c/ec23855274a73906b02f0d124fefd9cb3c008b1d
Raw JSON (NVD)
Show
{
"id": "CVE-2026-98548",
"cveTags": [],
"metrics": {},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"lessThan": "c0af3fd150fdc43821df3bb77e5ec74faf4dfc7a",
"versionType": "git"
},
{
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"lessThan": "854c053c71459f8db7ef07db9cfa4eec5f5206f2",
"versionType": "git"
},
{
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"versionType": "git"
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{
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"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
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"versionType": "git"
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{
"status": "affected",
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"versionType": "git"
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{
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"lessThan": "ec23855274a73906b02f0d124fefd9cb3c008b1d",
"versionType": "git"
},
{
"status": "affected",
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{
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"versionType": "git"
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],
"programFiles": [
"net/sctp/sm_statefuns.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.12"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "2.6.12",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.271",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.222",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.189",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.158",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.112",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.55",
"versionType": "semver",
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},
{
"status": "unaffected",
"version": "7.2.9",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/sctp/sm_statefuns.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-10-18T16:17:06.767",
"references": [
{
"url": "https://git.kernel.org/stable/c/1cd246b214dc9acf4e2f11d58c035e1e672fe7d2",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/4498467a8af06cfa3d71cb04bd7c4170dec8f449",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/6df536c5acbc0abd6f119d02e24f4a2ed97707f4",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/854c053c71459f8db7ef07db9cfa4eec5f5206f2",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/965e21ea16acb394d5e5801998ca9b0adc669665",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/c0af3fd150fdc43821df3bb77e5ec74faf4dfc7a",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/d68c9287b3ca0d6faadc61fbcb18d1a6b5493321",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/ec23855274a73906b02f0d124fefd9cb3c008b1d",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"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->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."
}
],
"lastModified": "2026-10-19T10:19:10.887",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}