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CVE-2026-31684— net: sched: act_csum: validate nested VLAN headers

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于act_csum中嵌套VLAN标头未确保线性存在，可能导致读取线性区域外数据及skb_pull违反不变量。

AI Predicted 7.5 Difficulty: Moderate EPSS 0.12% · P2

Possible ATT&CK Techniques 1 AI

T1564.008 · Email Hiding Rules

Affected Version Matrix 20

VendorProduct Version RangeStatus
Linux Linux 2ecba2d1e45b24620a7c3df9531895cf68d5dec6< 0410c619e86551677fb79887a38eccad3f5a0725 affected
2ecba2d1e45b24620a7c3df9531895cf68d5dec6< 886469b6455611a511aa6013e957e15e50577513 affected
2ecba2d1e45b24620a7c3df9531895cf68d5dec6< 46c07ad50fa2f4ba7663ee1b72b75ad7ad45cf09 affected
2ecba2d1e45b24620a7c3df9531895cf68d5dec6< eb3765b90eb8f2a3d6310a80c14a9e57ec4267a2 affected
2ecba2d1e45b24620a7c3df9531895cf68d5dec6< a69738efea0996d05a3c7d2178551b891744df1b affected
2ecba2d1e45b24620a7c3df9531895cf68d5dec6< ec4930979b3f7bbeb7af5744599fc6603a4dba62 affected
2ecba2d1e45b24620a7c3df9531895cf68d5dec6< 3d165d975305cf76ff0b10a3c798fb31e5f5f9a5 affected
2ecba2d1e45b24620a7c3df9531895cf68d5dec6< c842743d073bdd683606cb414eb0ca84465dd834 affected
… +12 more rows
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I. Basic Information for CVE-2026-31684

Vulnerability Information
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Vulnerability Title
net: sched: act_csum: validate nested VLAN headers
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于act_csum中嵌套VLAN标头未确保线性存在，可能导致读取线性区域外数据及skb_pull违反不变量。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 ~ 0410c619e86551677fb79887a38eccad3f5a0725 -
Linux Linux 5.1 -

II. Public POCs for CVE-2026-31684

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III. Intelligence Information for CVE-2026-31684

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Patches & Fixes for CVE-2026-31684 (4)

Same Patch Batch · Linux · 2026-04-25 · 13 CVEs total

CVE-2026-31685 9.4 CRITICAL netfilter: ip6t_eui64: reject invalid MAC header for all packets
CVE-2026-31682 9.1 CRITICAL bridge: br_nd_send: linearize skb before parsing ND options
CVE-2026-31683 7.8 HIGH batman-adv: avoid OGM aggregation when skb tailroom is insufficient
CVE-2026-31680 7.8 HIGH net: ipv6: flowlabel: defer exclusive option free until RCU teardown
CVE-2026-31678 7.8 HIGH openvswitch: defer tunnel netdev_put to RCU release
CVE-2026-31675 7.8 HIGH net/sched: sch_netem: fix out-of-bounds access in packet corruption
CVE-2026-31673 7.8 HIGH af_unix: read UNIX_DIAG_VFS data under unix_state_lock
CVE-2026-31676 7.5 HIGH rxrpc: only handle RESPONSE during service challenge
CVE-2026-31679 7.1 HIGH openvswitch: validate MPLS set/set_masked payload length
CVE-2026-31674 7.1 HIGH netfilter: ip6t_rt: reject oversized addrnr in rt_mt6_check()
CVE-2026-31681 netfilter: xt_multiport: validate range encoding in checkentry
CVE-2026-31677 crypto: af_alg - limit RX SG extraction by receive buffer budget

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-31684

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