CVE-2021-47291

Kernel memory disclosure and crash via route cleanup

Published May 21, 2024 · Updated Aug 5, 2026

An out-of-bounds read in the Linux IPv6 routing code allows local users to disclose kernel memory or interrupt the system. When fib6_metrics initialization fails for a caller-supplied nexthop, cleanup sends a half-initialized route to fib6_info_release, which reads beyond the slab allocation. Exploitation requires low-privileged local access and the ability to exercise IPv6 nexthop route handling; the bounded effects are memory disclosure and a kernel crash.

CVSS severity7.8
High
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

An out-of-bounds read in the Linux IPv6 routing code allows local users to disclose kernel memory or interrupt the system. When fib6_metrics initialization fails for a caller-supplied nexthop, cleanup sends a half-initialized route to fib6_info_release, which reads beyond the slab allocation. Exploitation requires low-privileged local access and the ability to exercise IPv6 nexthop route handling; the bounded effects are memory disclosure and a kernel crash.

The record

CVE
CVE-2021-47291
Published
May 21, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-125
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 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

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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=5.3
  2. Affected versionversion=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <115784bcccf135c3a3548098153413d76f16aae0
  3. Affected versionversion=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <830251361425c5be044db4d826aaf304ea3d14c6
  4. Affected versionversion=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <8fb4792f091e608a0a1d353dfdf07ef55a719db5
  5. Affected versionversion=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <ce8fafb68051fba52546f8bbe8621f7641683680

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.3; version=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <115784bcccf135c3a3548098153413d76f16aae0; version=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <830251361425c5be044db4d826aaf304ea3d14c6; version=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <8fb4792f091e608a0a1d353dfdf07ef55a719db5; version=f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <ce8fafb68051fba52546f8bbe8621f7641683680

Published CVSS scores

7.8Linux Kernel CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.1NIST National Vulnerability DatabaseCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read

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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