GHSA-365H-H8V6-R47M
Vulnerability from github – Published: 2026-10-18 18:31 – Updated: 2026-10-18 18:31In the Linux kernel, the following vulnerability has been resolved:
ipv6: sr: enforce exact attribute length for SEG6_ATTR_DST
In seg6_genl_policy, SEG6_ATTR_DST is defined with .type = NLA_BINARY and .len = sizeof(struct in6_addr). For NLA_BINARY, .len only enforces the maximum payload length and permits shorter payloads (e.g., 0 bytes). When seg6_genl_set_tunsrc() copies sizeof(struct in6_addr) bytes via kmemdup(val, sizeof(*val), GFP_KERNEL), a short SEG6_ATTR_DST attribute triggers a 16-byte out-of-bounds read past skb->tail into uninitialized skb->head memory, which is stored in sdata->tun_src and leaked back to userspace via SEG6_CMD_GET_TUNSRC.
Switch SEG6_ATTR_DST in seg6_genl_policy to NLA_POLICY_EXACT_LEN(sizeof(struct in6_addr)) so that generic netlink validation rejects any attribute whose length is not exactly sizeof(struct in6_addr) with -ERANGE.
Tested in QEMU against Linux 7.3.0-rc3 by sending a SEG6_CMD_SET_TUNSRC Generic Netlink message with a 0-byte SEG6_ATTR_DST attribute followed by SEG6_CMD_GET_TUNSRC. On the unfixed kernel, SEG6_CMD_SET_TUNSRC succeeds (err = 0) and SEG6_CMD_GET_TUNSRC leaks 16 bytes of uninitialized kernel heap memory (tun_src = 836a61ecc4d25a1042a8d60411cfb378); with this patch applied, SEG6_CMD_SET_TUNSRC is rejected by netlink policy validation with -ERANGE (-34) and tun_src remains zeroed.
{
"affected": [],
"aliases": [
"CVE-2026-98531"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-10-18T16:17:04Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: sr: enforce exact attribute length for SEG6_ATTR_DST\n\nIn seg6_genl_policy, SEG6_ATTR_DST is defined with .type = NLA_BINARY and\n.len = sizeof(struct in6_addr). For NLA_BINARY, .len only enforces the\nmaximum payload length and permits shorter payloads (e.g., 0 bytes).\nWhen seg6_genl_set_tunsrc() copies sizeof(struct in6_addr) bytes via\nkmemdup(val, sizeof(*val), GFP_KERNEL), a short SEG6_ATTR_DST attribute\ntriggers a 16-byte out-of-bounds read past skb-\u003etail into uninitialized\nskb-\u003ehead memory, which is stored in sdata-\u003etun_src and leaked back to\nuserspace via SEG6_CMD_GET_TUNSRC.\n\nSwitch SEG6_ATTR_DST in seg6_genl_policy to\nNLA_POLICY_EXACT_LEN(sizeof(struct in6_addr)) so that generic netlink\nvalidation rejects any attribute whose length is not exactly\nsizeof(struct in6_addr) with -ERANGE.\n\nTested in QEMU against Linux 7.3.0-rc3 by sending a SEG6_CMD_SET_TUNSRC\nGeneric Netlink message with a 0-byte SEG6_ATTR_DST attribute followed\nby SEG6_CMD_GET_TUNSRC. On the unfixed kernel, SEG6_CMD_SET_TUNSRC\nsucceeds (err = 0) and SEG6_CMD_GET_TUNSRC leaks 16 bytes of\nuninitialized kernel heap memory (tun_src =\n836a61ecc4d25a1042a8d60411cfb378); with this patch applied,\nSEG6_CMD_SET_TUNSRC is rejected by netlink policy validation with\n-ERANGE (-34) and tun_src remains zeroed.",
"id": "GHSA-365h-h8v6-r47m",
"modified": "2026-10-18T18:31:52Z",
"published": "2026-10-18T18:31:52Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98531"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/050a0aa3c80907b8c60a396b7e04d48d8b1a9e70"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/195813bb7324c338eaba0aaa02b18681ee65b670"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/209eefebee54c4a5f01d68b61e8ac9881eca2de9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2d959c75c27f90e9ec489d18ce5ee6b852ad4741"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/66bf65fa109326e4c4ddeb0b94093379f72838fd"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6fcfc362344edea745a69f3a705de50b731f3418"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/94214cf0a08dd2c5f37aeeea46078d9dfe8e4a0e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e3ac68c1cdc2535d127b2bfd50c263d16c8e4199"
}
],
"schema_version": "1.4.0",
"severity": []
}
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