Bug 2461566 (CVE-2026-31668)

Summary: CVE-2026-31668 kernel: seg6: separate dst_cache for input and output paths in seg6 lwtunnel
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: rhel-process-autobot, 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 Segment Routing over IPv6 (SRv6) lightweight tunnel (seg6 lwtunnel). This component incorrectly shares a single destination cache between its input and output processing paths. This allows one path to reuse cached routing information populated by the other, bypassing its own independent routing context lookup. This can lead to unintended routing behavior or a bypass of network policy enforcement, potentially impacting network traffic integrity.
 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 2026-04-24 15:08:49 UTC 
In the Linux kernel, the following vulnerability has been resolved:

seg6: separate dst_cache for input and output paths in seg6 lwtunnel

The seg6 lwtunnel uses a single dst_cache per encap route, shared
between seg6_input_core() and seg6_output_core(). These two paths
can perform the post-encap SID lookup in different routing contexts
(e.g., ip rules matching on the ingress interface, or VRF table
separation). Whichever path runs first populates the cache, and the
other reuses it blindly, bypassing its own lookup.

Fix this by splitting the cache into cache_input and cache_output,
so each path maintains its own cached dst independently.
Comment 1 Keith Grant 2026-04-24 22:35:01 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026042406-CVE-2026-31668-50e7@gregkh/T