CVE-2021-47126

Kernel crash via unallocated IPv6 nexthop release

Published Mar 15, 2024 · Updated Aug 5, 2026

Out-of-bounds read in Linux IPv6 routing allows local users to crash the kernel through crafted route updates over rtnetlink. When ip6_route_info_create receives a nexthop pointer without allocating the fib6_nh array, its failure path releases a nonexistent array element and reads adjacent slab memory. Triggering the path requires CAP_NET_ADMIN for RTM_NEWROUTE, obtainable in enabled user and network namespaces, and the invalid values can drive a kernel oops or panic.

CVSS severity5.5
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

Out-of-bounds read in Linux IPv6 routing allows local users to crash the kernel through crafted route updates over rtnetlink. When ip6_route_info_create receives a nexthop pointer without allocating the fib6_nh array, its failure path releases a nonexistent array element and reads adjacent slab memory. Triggering the path requires CAP_NET_ADMIN for RTM_NEWROUTE, obtainable in enabled user and network namespaces, and the invalid values can drive a kernel oops or panic.

The record

CVE
CVE-2021-47126
Published
Mar 15, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-125, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 15, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=5.3
  2. Affected versionversion=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <09870235827451409ff546b073d754a19fd17e2e
  3. Affected versionversion=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <0a462e25ef0f7ab305081a08d435bbd1f13c0a94
  4. Affected versionversion=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <7ba7fa78a92dc410b6f93ed73075ab669c3a0b59
  5. Affected versionversion=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <821bbf79fe46a8b1d18aa456e8ed0a3c208c3754

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.3; version=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <09870235827451409ff546b073d754a19fd17e2e; version=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <0a462e25ef0f7ab305081a08d435bbd1f13c0a94; version=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <7ba7fa78a92dc410b6f93ed73075ab669c3a0b59; version=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <821bbf79fe46a8b1d18aa456e8ed0a3c208c3754

Published CVSS scores

5.5SUSECVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.8NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8Linux Kernel CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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