CVE-2026-31668
Description
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.
Statement
The patch fixes a routing logic flaw in the SRv6 seg6 lwtunnel implementation. Previously, each encap route had a single dst_cache stored in struct seg6_lwt. That cache was shared by both seg6_input_core and seg6_output_core. These two code paths may perform the post encapsulation SID lookup under different routing contexts such as rules that match on the ingress interface or VRF based table selection. With one shared cache, whichever path executed first populated the cache. The other path then reused the cached dst blindly and could bypass its own lookup. This is best classified as a logic or policy enforcement issue rather than memory corruption.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 3.3 | N/A | 9.8 |
| Attack Vector | Local | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | High |
| Integrity Impact | Low | N/A | High |
| Availability Impact | None | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity,Confidentiality,Other
Technical Impact: Modify Application Data; Read Application Data; Alter Execution Logic
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