CVE-2021-47515

Host crash via erased receiving-interface index

Published May 24, 2024 · Updated Aug 5, 2026

NULL pointer dereference in the Linux kernel's IPv6 SRv6 encapsulation path allows local users to crash the host with crafted IPv4 traffic. seg6_do_srh_encap clears the shared socket control block, erasing the receiving-interface index before forwarding statistics dereference it. Reachability requires SRv6 IPv4-in-IPv6 encapsulation and the affected forwarding-statistics change; the bounded consequence is a kernel crash.

CVSS severity5.5
Medium
EPSS probability0.75%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in the Linux kernel's IPv6 SRv6 encapsulation path allows local users to crash the host with crafted IPv4 traffic. seg6_do_srh_encap clears the shared socket control block, erasing the receiving-interface index before forwarding statistics dereference it. Reachability requires SRv6 IPv4-in-IPv6 encapsulation and the affected forwarding-statistics change; the bounded consequence is a kernel crash.

The record

CVE
CVE-2021-47515
Published
May 24, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 24, 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=2f704348c93ff8119e642dae6a72327f90b82810 <6431e71093f3da586a00c6d931481ffb0dc2db0e
  2. Affected versionversion=4.14.98 <4.14.258
  3. Affected versionversion=4.19.20 <4.19.221
  4. Affected versionversion=4.20.7 <4.21
  5. Affected versionversion=5.0
  6. Affected versionversion=b71b7e0280f47b4ac633fbfd153423814ea87810
  7. Affected versionversion=c630ec8bdadae9d557b1ceb9d6c06e149108a0d4 <b16d412e5f79734033df04e97d7ea2f50a8e9fe3
  8. Affected versionversion=ef489749aae508e6f17886775c075f12ff919fb1 <666521b3852d2b2f52d570f9122b1e4b50d96831
  9. Affected versionversion=ef489749aae508e6f17886775c075f12ff919fb1 <98adb2bbfa407c9290bda299d4c6f7a1c4ebd5e1
  10. Affected versionversion=ef489749aae508e6f17886775c075f12ff919fb1 <ae68d93354e5bf5191ee673982251864ea24dd5c
  11. Affected versionversion=ef489749aae508e6f17886775c075f12ff919fb1 <ef8804e47c0a44ae106ead1740408af5ea6c6ee9

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2f704348c93ff8119e642dae6a72327f90b82810 <6431e71093f3da586a00c6d931481ffb0dc2db0e; version=4.14.98 <4.14.258; version=4.19.20 <4.19.221; version=4.20.7 <4.21; version=5.0; version=b71b7e0280f47b4ac633fbfd153423814ea87810; version=c630ec8bdadae9d557b1ceb9d6c06e149108a0d4 <b16d412e5f79734033df04e97d7ea2f50a8e9fe3; version=ef489749aae508e6f17886775c075f12ff919fb1 <666521b3852d2b2f52d570f9122b1e4b50d96831; version=ef489749aae508e6f17886775c075f12ff919fb1 <98adb2bbfa407c9290bda299d4c6f7a1c4ebd5e1; version=ef489749aae508e6f17886775c075f12ff919fb1 <ae68d93354e5bf5191ee673982251864ea24dd5c; version=ef489749aae508e6f17886775c075f12ff919fb1 <ef8804e47c0a44ae106ead1740408af5ea6c6ee9

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
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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