VulnSocial

CVE-2026-31684Disclosure(linux / linux_kernel)

LOWCVSS 5.5 · MEDIUM

Signal is active with 1 mentions in latest observed window

Immediate actions

  • Patch linux linux_kernel systems immediately

Recommended action window: Monitor and triage in normal cycle

NVD description

In the Linux kernel, the following vulnerability has been resolved: net: sched: act_csum: validate nested VLAN headers tcf_csum_act() walks nested VLAN headers directly from skb->data when an skb still carries in-payload VLAN tags. The current code reads vlan->h_vlan_encapsulated_proto and then pulls VLAN_HLEN bytes without first ensuring that the full VLAN header is present in the linear area. If only part of an inner VLAN header is linearized, accessing h_vlan_encapsulated_proto reads past the linear area, and the following skb_pull(VLAN_HLEN) may violate skb invariants. Fix this by requiring pskb_may_pull(skb, VLAN_HLEN) before accessing and pulling each nested VLAN header. If the header still is not fully available, drop the packet through the existing error path.

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0.5/ 10 priority

Sources & remediation

Patch / fix
Other references

Priority

LOW

Exploitation

NONE

PoC

NONE

Patch

AVAILABLE

Momentum

STABLE

Are you affected?

If you run products in this scope, you should treat this CVE as relevant to your environment.

  • linux_kernel

Threat summary

  • Patch or workaround signal is available
  • 3 mentions across 2 observed days
  • Momentum state: stable

What's happening

  • Patch or workaround mentioned in 1 signal
  • Technical details provided in 3 signals
  • Disclosure: 2 classified signals
  • Peaked 1d ago at 2 mentions (2026-04-25); latest day: 1
  • 3 total mentions across 2 days

Affected systems

Vendors
linux
Products
linux_kernel

1 version affected across 1 product

Deep dive

Activity timeline3 mentions / 2d
01122Mentions · 2026-04-25: 2Mentions · 2026-04-26: 1Patch / Workaround · 2026-04-25: 1Technical Details · 2026-04-25: 2Technical Details · 2026-04-26: 104-2504-26
Signal classification2 categories
Disclosure
266.7%
Patch
133.3%
Referenced assets3 URLs
Classification over time
DateTotalLabels
2026-04-252
Disclosure1Patch1
2026-04-261
Disclosure1
Full discourse3 posts
  • WindowsForum@windowsforum
    Disclosure

    🪟 CVE-2026-31684 is a “tiny” Linux kernel packet-checksum bug—until your WSL boxes start faceplanting on weird VLAN traffic. Microsoft: triage WSL like it’s prod, not lab. https://windowsforum.com/threads/cve-2026-31684-linux-kernel-act_csum-vlan-bug-windows-teams-should-triage-wsl.415307/?utm_source=x&utm_medium=social&utm_campaign=news_node84 #TrafficControl #LinuxKernelSecurity #VlanNetworking #Wsl2 https://t.co/bDZi6dTubZ

    Post summary

    The tweet announces CVE-2026-31684 as a Linux kernel packet‑checksum bug that could crash WSL when handling VLAN traffic, but it provides no PoC, exploit, or mitigation details.

    0000097
    1.1K followersView on X
  • CVE@CVEnew
    Patch

    CVE-2026-31684 In the Linux kernel, the following vulnerability has been resolved: net: sched: act_csum: validate nested VLAN headers tcf_csum_act() walks nested VLAN headers dire… https://www.cve.org/CVERecord?id=CVE-2026-31684

    Post summary

    The entry notes that CVE-2026-31684, a Linux kernel issue involving nested VLAN header validation in the net scheduler, has been fixed; no PoC, exploit, or active exploitation is reported.

    0000059
    57.2K followersView on X
  • Vulmon Vulnerability Feed@VulmonFeeds
    Disclosure

    CVE-2026-31684 Linux Kernel VLAN Header Validation Vulnerability in net.sched.act_csum https://vulmon.com/vulnerabilitydetails?qid=CVE-2026-31684

    Post summary

    A new Linux kernel VLAN header validation vulnerability (CVE-2026-31684) has been disclosed, with minimal details and no evidence of exploitation or mitigation.

    0000049
    4.0K followersView on X
CPE platform detail8 entries

8 of 8 entries

PartVendorProductVersionTarget SWTarget HW
OSlinuxlinux_kernel---
OSlinuxlinux_kernel7.0--
OSlinuxlinux_kernel7.0--
OSlinuxlinux_kernel7.0--
OSlinuxlinux_kernel7.0--
OSlinuxlinux_kernel7.0--
OSlinuxlinux_kernel7.0--
OSlinuxlinux_kernel7.0--

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