GHSA-X4FQ-3FW2-872X
Vulnerability from github – Published: 2026-10-18 18:31 – Updated: 2026-10-30 15:33In the Linux kernel, the following vulnerability has been resolved:
net: ipconfig: bound DHCP option construction
ic_dhcp_init_options() appends the hostname (option 12), vendor-class (option 60) and client-ID (option 61) options into the fixed 312-byte bootp_pkt.exten[] buffer. Only the client-ID branch checked the remaining space; the hostname and vendor-class writes were unbounded.
A 64-byte hostname together with the maximum 252-byte dhcpclass= identifier needs 18 + (2 + 64) + (2 + 252) = 338 of the 312 available bytes even before the terminating END marker, so the vendor-class memcpy runs past the end of exten[]. With CONFIG_FORTIFY_SOURCE this is reported as a field-spanning write and, when the kernel is booted with panic_on_warn=1, aborts boot with a panic.
Route the optional options through a common helper that makes sure the option, its 2-byte header and the END marker all fit and drops an option that would not. Configurations with short options keep sending exactly the same bytes as before.
{
"affected": [],
"aliases": [
"CVE-2026-98493"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-10-18T16:17:00Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipconfig: bound DHCP option construction\n\nic_dhcp_init_options() appends the hostname (option 12), vendor-class\n(option 60) and client-ID (option 61) options into the fixed 312-byte\nbootp_pkt.exten[] buffer. Only the client-ID branch checked the\nremaining space; the hostname and vendor-class writes were unbounded.\n\nA 64-byte hostname together with the maximum 252-byte dhcpclass=\nidentifier needs 18 + (2 + 64) + (2 + 252) = 338 of the 312 available\nbytes even before the terminating END marker, so the vendor-class memcpy\nruns past the end of exten[]. With CONFIG_FORTIFY_SOURCE this is\nreported as a field-spanning write and, when the kernel is booted with\npanic_on_warn=1, aborts boot with a panic.\n\nRoute the optional options through a common helper that makes sure the\noption, its 2-byte header and the END marker all fit and drops an option\nthat would not. Configurations with short options keep sending exactly\nthe same bytes as before.",
"id": "GHSA-x4fq-3fw2-872x",
"modified": "2026-10-30T15:33:53Z",
"published": "2026-10-18T18:31:51Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98493"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/24e79508b237dd2a69bc6fb6ac5cf7f126178307"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/38a6a118260ebfc82d0c653194d616bdfbd236ac"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/abcba6f080c63e403037ecdffde43170d242376a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ca811550b9fa87e02845b4a332d194c2304d933f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cbaad2922bd5d4d303055ae9afecc8999e6b40c9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d8016c82acdd7eaa462e1f38a962b15d8c6a650b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e0a221cec0e0ee437680ae0314a4b166509442c5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e47a1958e12abc3a17b5231a4f21c8f1bf662e08"
}
],
"schema_version": "1.4.0",
"severity": []
}
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