Bug 2348539 (CVE-2025-21768)

Summary:	CVE-2025-21768 kernel: net: ipv6: fix dst ref loops in rpl, seg6 and ioam6 lwtunnels
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	dfreiber, drow, jburrell, vkumar
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:	This is a memory leak vulnerability in the Linux kernel's Lightweight Tunnel (lwtunnel) subsystem. When triggered, it causes the lwtunnel state to never be freed, leading to gradual memory consumption over time. This can result in system performance degradation or resource exhaustion if the condition persists.	Story Points:	---
Clone Of:		Environment:
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Regression:	---	Mount Type:	---
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Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2025-02-27 03:02:29 UTC

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

net: ipv6: fix dst ref loops in rpl, seg6 and ioam6 lwtunnels

Some lwtunnels have a dst cache for post-transformation dst.
If the packet destination did not change we may end up recording
a reference to the lwtunnel in its own cache, and the lwtunnel
state will never be freed.

Discovered by the ioam6.sh test, kmemleak was recently fixed
to catch per-cpu memory leaks. I'm not sure if rpl and seg6
can actually hit this, but in principle I don't see why not.

Comment 1 Michal Findra 2025-02-27 16:21:10 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025022605-CVE-2025-21768-512b@gregkh/T