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net: ipconfig: bound DHCP option construction

Type: advisorySources: OSV

In 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.

Products
Kernel
Affected versions
Not specified
Fixed versions
5.10.273, 5.15.224, 6.1.191, 6.12.112, 6.18.55, 6.6.160, 7.2.9
CVEs
CVE-2026-98493
Confirmed fixed CVEs
Not specified
Updated in this feed
6 Nov 2026, 02:36 UTC · Revision 1

Source evidence

net: ipconfig: bound DHCP option construction

core-osv · Original source

Published 18 Oct 2026, 15:16 UTC

In 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.

osv:CVE-2026-98493

Kernel

Fixed versions: 5.10.273, 5.15.224, 6.1.191, 6.6.160, 6.12.112, 6.18.55, 7.2.9

Complete source record
{
  "id": "406d7ee0cb9bb819e6f183c438b933a81d0aeae071e62d56ff0871f384289a07",
  "url": "https://osv.dev/vulnerability/CVE-2026-98493",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "net: ipconfig: bound DHCP option construction",
    "summary": "In 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.",
    "evidence": "osv:CVE-2026-98493",
    "products": [
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        "prerequisites": [],
        "fixed_versions": [
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            "evidence": "/affected/1/ranges"
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            "evidence": "/affected/1/ranges"
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          {
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            "evidence": "/affected/1/ranges"
          },
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            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.112",
            "evidence": "/affected/1/ranges"
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            "evidence": "/affected/1/ranges"
          }
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        "affected_versions": []
      }
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    "severity": "unknown",
    "structured": {
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      "aliases": [
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              "type": "ECOSYSTEM",
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                  "introduced": "2.6.36"
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                  "introduced": "5.11.0"
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              "type": "ECOSYSTEM",
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                  "introduced": "5.16.0"
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            "ecosystem": "Linux"
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      ],
      "modified": "2026-11-01T02:30:41.098462370Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/24e79508b237dd2a69bc6fb6ac5cf7f126178307",
        "https://git.kernel.org/stable/c/38a6a118260ebfc82d0c653194d616bdfbd236ac",
        "https://git.kernel.org/stable/c/abcba6f080c63e403037ecdffde43170d242376a",
        "https://git.kernel.org/stable/c/ca811550b9fa87e02845b4a332d194c2304d933f",
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        "https://git.kernel.org/stable/c/e47a1958e12abc3a17b5231a4f21c8f1bf662e08",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98493.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-98493",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98493.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-98493",
        "evidence": "/id"
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    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 514335,
  "published_at": "2026-10-18T15:16:22.301+00:00"
}