Bug 2554885 (CVE-2026-98493)

Summary: CVE-2026-98493 kernel: net: ipconfig: bound DHCP option construction
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel. This vulnerability allows an attacker capable of specifying system boot or network parameters to cause a Denial of Service (DoS) or memory corruption. During Dynamic Host Configuration Protocol (DHCP) autoconfiguration, the kernel appends options into a fixed-size buffer without verifying available space for hostname and vendor class identifiers. Supplying oversized configuration parameters triggers an out-of-bounds memory write, which can abort the boot process with a kernel panic.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-10-18 15:25:20 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.
Comment 1 Mauro Matteo Cascella 2026-10-20 13:13:00 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98493.mbox