CVE-2021-3635

Kernel panic via duplicate flowtable deletion

Published Aug 13, 2021 · Updated Aug 3, 2024

Memory corruption in Linux kernel netfilter before 5.5-rc7 allows local users with CAP_SYS_ADMIN to panic the system via an nftables transaction. During DELTABLE processing, a missing generation check queues deletion of the same flowtable twice, causing nf_tables_commit to call list_del_rcu twice on one list node. Root or CAP_SYS_ADMIN access is required, and exploitation crashes the kernel without a reported confidentiality or integrity impact.

CVSS severity4.1
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in Linux kernel netfilter before 5.5-rc7 allows local users with CAP_SYS_ADMIN to panic the system via an nftables transaction. During DELTABLE processing, a missing generation check queues deletion of the same flowtable twice, causing nf_tables_commit to call list_del_rcu twice on one list node. Root or CAP_SYS_ADMIN access is required, and exploitation crashes the kernel without a reported confidentiality or integrity impact.

The record

CVE
CVE-2021-3635
Published
Aug 13, 2021
Updated
Aug 3, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-119, T1499.004
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Aug 13, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=kernel 5.5-rc7

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linux Kernelversion=kernel 5.5-rc7

Published CVSS scores

4.1Red HatCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
4.9NIST NVDAV:L/AC:L/Au:N/C:N/I:N/A:C
4.4NIST NVDCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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