Out-of-bounds write in Linux kernel - CVE-2026-98493

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Main Vulnerability Database Vulnerabilities #VU156793

Out-of-bounds write in Linux kernel - CVE-2026-98493

Published: October 22, 2026


Vulnerability identifier: #VU156793
CSH Severity: Low
CVSS v4: 6.7 [CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-98493
CWE-ID: CWE-787
Exploitation vector: Local access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a local privileged user to cause a denial of service during Linux kernel boot.

The vulnerability exists due to an out-of-bounds write in ic_dhcp_init_options() in net/ipv4/ipconfig.c when constructing boot-time DHCP options without checking the space remaining for hostname and vendor-class values. A local privileged user can supply a combination of hostname and dhcpclass= values that exceeds the fixed 312-byte bootp_pkt.exten[] buffer to overwrite adjacent memory and disrupt boot, including triggering a kernel panic when CONFIG_FORTIFY_SOURCE and panic_on_warn=1 are enabled.


Affected software

Linux kernel
Ubuntu
linux (Ubuntu package)
linux-aws (Ubuntu package)
linux-gcp (Ubuntu package)
linux-oracle (Ubuntu package)
linux-ibm (Ubuntu package)
linux-hwe-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)

How to mitigate CVE-2026-98493

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux (Ubuntu package) - update to 7.0.0-42.42
linux-aws (Ubuntu package) - update to 7.0.0-1016.17
linux-gcp (Ubuntu package) - update to 7.0.0-1016.18
linux-oracle (Ubuntu package) - update to 7.0.0-1015.16
linux-ibm (Ubuntu package) - update to 7.0.0-1017.17
linux-hwe-7.0 (Ubuntu package) - update to 7.0.0-42.42~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1017.17

External References

Related Security Bulletins