Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1336 CNY

100%
Buy Us a Coffee

CVE-2026-80634— netfilter: flowtable: avoid num_encaps underflow on bridge VLAN untag

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.

以下是该漏洞描述的中文翻译： 在 Linux 内核中，已修复以下漏洞： netfilter: flowtable: 在网桥 VLAN 去标签（untag）时避免 num_encaps 下溢 在 分支中，代码在 宏内部对 进行后自减（post-decrement）。由于 是无符号 8 位整数（u8），如果其值已经为 0，自减操作仍会执行，导致数值环绕回绕为 255。 语句仅使程序跳出内部的 语句块，但后续的路径条目可能会将 重新设置为一个真实的网络设备，最终导致函数返回时 。 随后， 函数会遍历 （大小为 2），遍历

CVSS 9.8 · Critical EPSS 0.15% · P5

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 6

VendorProduct Version RangeStatus
Linux Linux e990cef6516daa4e1e236433579e333f74fd38cb< 2f55fa28011c97d6495d5787808db10a8c2d690d affected
e990cef6516daa4e1e236433579e333f74fd38cb< e052f920773b73be49eb4d8702a9f85de7464363 affected
5.13 affected
< 5.13 unaffected
7.1.5≤ 7.1.* unaffected
7.2≤ * unaffected
Get alerts for future matching vulnerabilities Log in to subscribe

I. Basic Information for CVE-2026-80634

Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
netfilter: flowtable: avoid num_encaps underflow on bridge VLAN untag
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: netfilter: flowtable: avoid num_encaps underflow on bridge VLAN untag The DEV_PATH_BR_VLAN_UNTAG case post-decrements info->num_encaps inside WARN_ON_ONCE(). num_encaps is u8, so if it's already 0 the decrement still happens and wraps it to 255. The break only leaves the inner switch -- a later path entry can set info->indev back to a real device, and we end up returning with num_encaps == 255. nft_dev_forward_path() then walks info.encap[] (size 2) up to num_encaps, which means an OOB stack read and a bogus count copied into the route descriptor. Should only happen on a malformed bridge path stack, hence the WARN, but worth handling sanely. Move the decrement out of the WARN. [ While at this, remove the WARN_ON_ONCE since this can only happen with a buggy bridge path stack --pablo ].
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux e990cef6516daa4e1e236433579e333f74fd38cb ~ 2f55fa28011c97d6495d5787808db10a8c2d690d -
Linux Linux 5.13 -

II. Public POCs for CVE-2026-80634

# POC Description Source Link Shenlong Link
AI-Generated POC Premium

No public POC found.

Login to generate AI POC

III. Intelligence Information for CVE-2026-80634

请登录查看更多情报信息。

Patches & Fixes for CVE-2026-80634 (2)

Same Patch Batch · Linux · 2026-08-28 · 135 CVEs total

CVE-2026-80694 9.8 CRITICAL net: ethernet: mtk_eth_soc: pass eth to mtk_handle_irq_rx in poll_controller
CVE-2026-80668 9.8 CRITICAL netfilter: nf_conntrack_expect: use conntrack GC to reap expectations
CVE-2026-80673 9.8 CRITICAL ntfs: bound the look-ahead attribute-list entry in ntfs_external_attr_find()
CVE-2026-80674 9.8 CRITICAL ntfs: validate resident attribute lists and harden the validator
CVE-2026-80630 9.8 CRITICAL net/sched: sch_fq_codel: Do not call qdisc_tree_reduce_backlog during peek before restorin
CVE-2026-80617 9.8 CRITICAL net: airoha: fix foe_check_time allocation size
CVE-2026-80612 9.8 CRITICAL net: lwtunnel: Drop skb metadata before LWT encapsulation
CVE-2026-80714 9.8 CRITICAL ipvs: do not propagate one-packet flag to synced conns
CVE-2026-80609 9.8 CRITICAL qede: fix out-of-bounds check for cqe->len_list[]
CVE-2026-80681 9.8 CRITICAL vxlan: re-fetch eth header after route_shortcircuit()
CVE-2026-80600 9.8 CRITICAL batman-adv: dat: acquire ARP hw source only after skb realloc
CVE-2026-80671 9.3 CRITICAL perf sched: Fix register_pid() overflow, strcpy, and BUG_ON
CVE-2026-80693 9.3 CRITICAL idpf: bound interrupt-vector register fill to the allocated array
CVE-2026-80684 9.3 CRITICAL KVM: s390: pci: Fix NULL dereference on AIBV allocation failure
CVE-2026-80603 9.1 CRITICAL netfilter: nf_conntrack_irc: fix parse_dcc() off-by-one OOB read
CVE-2026-80670 9.1 CRITICAL perf tools: Use perf_env__get_cpu_topology() in machine__resolve()
CVE-2026-80683 8.8 HIGH Bluetooth: SCO: give the socket its own sco_conn reference
CVE-2026-80692 8.8 HIGH Bluetooth: hci_sync: hold conn in hci_connect_acl/le_sync() callbacks
CVE-2026-80633 8.8 HIGH iommufd: Take dma_resv lock before dma_buf_unpin() in release path
CVE-2026-80672 8.8 HIGH ntfs: fix u16 truncation of restart-area length check

Showing top 20 of 135 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-80634

No comments yet

Leave a comment