GHSA-F2R5-8634-VV9Q
Vulnerability from github – Published: 2026-09-25 12:31 – Updated: 2026-10-22 18:38In the Linux kernel, the following vulnerability has been resolved:
sctp: fix soft lockup from unpadded ASCONF-ACK parameter iteration
sctp_verify_asconf() walks ASCONF-ACK parameters with sctp_walk_params(), which advances by SCTP_PAD4(length), while the consumer sctp_get_asconf_response() iterates the same parameters advancing by the raw length, without padding. A single odd-length parameter desynchronises the two walks and makes the consumer interpret attacker-controlled bytes at a misaligned offset.
When those bytes yield a length of zero, the while loop over asconf_ack_len makes no progress, spinning forever in softirq context, and the watchdog reports a soft lockup. All reads stay within the received skb, so the lockup is a pure remote denial of service. A remote peer can trigger it with a crafted ASCONF-ACK on an ADD-IP enabled association with an outstanding ASCONF (RFC 5061 section 4.1.2 requires the chunk to be authenticated, but the predefined empty key id 0 allows the peer to compute the same association HMAC from publicly exchanged parameters, so the gate does not help).
The SCTP_PARAM_ERR_CAUSE case of sctp_verify_asconf() also performs no length check, letting a parameter without a complete error header reach the consumer, which reads errhdr.cause past the end of the parameter, an out-of-bounds read.
Reject SCTP_PARAM_ERR_CAUSE parameters shorter than sizeof(struct sctp_addip_param) + sizeof(struct sctp_errhdr) at the verifier, and advance the consumer iterator with the same padding rule as the verifier to keep the two walks in lockstep. The verifier change guarantees a complete error header in every ERR_CAUSE parameter the consumer can see, so the consumer's asconf_ack_len check is dropped and it returns err_param->cause directly. The consumer padding fix is still required because odd lengths remain valid for SCTP_PARAM_ERR_CAUSE per RFC 5061.
The issue was found by ZeroHive, a vulnerability hunting agent at Tencent Yunding Lab.
{
"affected": [],
"aliases": [
"CVE-2026-98123"
],
"database_specific": {
"cwe_ids": [
"CWE-667"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-25T11:17:43Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsctp: fix soft lockup from unpadded ASCONF-ACK parameter iteration\n\nsctp_verify_asconf() walks ASCONF-ACK parameters with\nsctp_walk_params(), which advances by SCTP_PAD4(length), while the\nconsumer sctp_get_asconf_response() iterates the same parameters\nadvancing by the raw length, without padding. A single odd-length\nparameter desynchronises the two walks and makes the consumer\ninterpret attacker-controlled bytes at a misaligned offset.\n\nWhen those bytes yield a length of zero, the while loop over\nasconf_ack_len makes no progress, spinning forever in softirq\ncontext, and the watchdog reports a soft lockup. All reads stay\nwithin the received skb, so the lockup is a pure remote denial of\nservice. A remote peer can trigger it with a crafted ASCONF-ACK on\nan ADD-IP enabled association with an outstanding ASCONF (RFC 5061\nsection 4.1.2 requires the chunk to be authenticated, but the\npredefined empty key id 0 allows the peer to compute the same\nassociation HMAC from publicly exchanged parameters, so the gate\ndoes not help).\n\nThe SCTP_PARAM_ERR_CAUSE case of sctp_verify_asconf() also performs\nno length check, letting a parameter without a complete error\nheader reach the consumer, which reads errhdr.cause past the end of\nthe parameter, an out-of-bounds read.\n\nReject SCTP_PARAM_ERR_CAUSE parameters shorter than\nsizeof(struct sctp_addip_param) + sizeof(struct sctp_errhdr) at the\nverifier, and advance the consumer iterator with the same padding\nrule as the verifier to keep the two walks in lockstep. The verifier\nchange guarantees a complete error header in every ERR_CAUSE\nparameter the consumer can see, so the consumer\u0027s asconf_ack_len\ncheck is dropped and it returns err_param-\u003ecause directly. The\nconsumer padding fix is still required because odd lengths remain\nvalid for SCTP_PARAM_ERR_CAUSE per RFC 5061.\n\nThe issue was found by ZeroHive, a vulnerability hunting agent at\nTencent Yunding Lab.",
"id": "GHSA-f2r5-8634-vv9q",
"modified": "2026-10-22T18:38:33Z",
"published": "2026-09-25T12:31:37Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98123"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2cb0b0b1ed69430bf73740377ea0a1c44c50db63"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3be02999ab9131a4b96eb1eda4ca48b1cea80f03"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4548d843e7b29f6d150d8caae4e64015fa226b0c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5fbc6a778d5fce7628821236972596acb18e1065"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7ba84e2971d208a2d6413a334ec28a8a32cdce0f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7d8e7ab6a0665888beee91f7ad77ac805963c4fd"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/abf59d7f6fff23227256e8199aca5ade45758f8b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ba54cad229977f4fae6355dbdaf117088414fdd0"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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