Bug 2532202 (CVE-2026-89562)

Summary:	CVE-2026-89562 kernel: ip6_gre: fix hardware header length for NBMA tunnels
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
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 Generic Routing Encapsulation (GRE) subsystem. The kernel incorrectly calculates the hardware header length for Non-Broadcast Multiple Access (NBMA) tunnel interfaces by improperly accumulating the underlying device's header length. A local authenticated attacker could exploit this flaw to trigger improper packet buffer handling, potentially leading to a Denial of Service (DoS) via a system crash.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-09-11 21:18:31 UTC

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

ip6_gre: fix hardware header length for NBMA tunnels

ip6gre_tnl_link_config_route() accumulates the lower device's hardware
header length into dev->hard_header_len whenever header_ops is set. This
is incorrect for both users of header_ops.

ip6gretap and ip6erspan have a fixed Ethernet hardware header length.
For an NBMA ip6gre tunnel, ip6gre_header() creates only the GRE header,
the optional FOU or GUE header, and the outer IPv6 header. The lower
device header is headroom needed later, not part of the tunnel device's
hardware header.

Keep the lower device header in needed_headroom. Set hard_header_len to
the tunnel header length only for ARPHRD_IP6GRE devices with header_ops,
and leave the fixed Ethernet header length unchanged for tap and erspan
devices.

Comment 1 Keith Grant 2026-09-18 15:50:07 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89562.mbox