Bug 2559824 (CVE-2026-99070)

Summary:	CVE-2026-99070 kernel: ipv6: do not warn on route notification size race
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	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
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's IPv6 subsystem. When nexthop compatibility mode is enabled, a race condition between sizing and populating route notification buffers can trigger an unexpected kernel warning. A local user could trigger this condition during concurrent route modifications, potentially leading to a Denial of Service (DoS) on systems configured to panic on kernel warnings.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
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Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-10-23 13:48:10 UTC

In the Linux kernel, the following vulnerability has been resolved:

ipv6: do not warn on route notification size race

fib6_info_hw_flags_set() sizes the skb with rt6_nlmsg_size() and later
fills it with rt6_fill_node().  With nexthop compatibility mode enabled,
a concurrent replacement can grow the group between these independent
snapshots.  rt6_fill_node() can then legitimately return -EMSGSIZE, so
the warning does not prove a sizing bug.

Remove the warning.  The existing error path still frees the skb and
reports the error to listeners.

Comment 1 gkamathe 2026-10-26 11:17:21 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-99070.mbox