CVE-2021-46999Network attack vector

Remote kernel crash via SCTP transport use-after-free

Published Feb 28, 2024 · Updated Aug 5, 2026

Use-after-free in the Linux kernel SCTP state machine allows remote attackers to crash the host through crafted SCTP association traffic. When sctp_sf_do_dupcook_a handles a duplicate COOKIE-ECHO, it allocates COOKIE-ACK and SHUTDOWN chunks against a new association but sends them through the old association, leaving shutdown_last_sent_to pointing to freed transport memory. Any remote SCTP peer that completes an association and controls the shutdown and restart exchange can trigger the later T2-timer dereference, causing a kernel panic.

CVSS severity9.8
Critical
EPSS probability0.74%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in the Linux kernel SCTP state machine allows remote attackers to crash the host through crafted SCTP association traffic. When sctp_sf_do_dupcook_a handles a duplicate COOKIE-ECHO, it allocates COOKIE-ACK and SHUTDOWN chunks against a new association but sends them through the old association, leaving shutdown_last_sent_to pointing to freed transport memory. Any remote SCTP peer that completes an association and controls the shutdown and restart exchange can trigger the later T2-timer dereference, causing a kernel panic.

The record

CVE
CVE-2021-46999
Published
Feb 28, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 28, 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=145cb2f7177d94bc54563ed26027e952ee0ae03c <0bfd913c2121b3d553bfd52810fe6061d542d625
  2. Affected versionversion=145cb2f7177d94bc54563ed26027e952ee0ae03c <35b4f24415c854cd718ccdf38dbea6297f010aae
  3. Affected versionversion=145cb2f7177d94bc54563ed26027e952ee0ae03c <61b877bad9bb0d82b7d8841be50872557090a704
  4. Affected versionversion=145cb2f7177d94bc54563ed26027e952ee0ae03c <f01988ecf3654f805282dce2d3bb9afe68d2691e
  5. Affected versionversion=4.19.123 <4.19.191
  6. Affected versionversion=5.4.41 <5.4.120
  7. Affected versionversion=5.6.13 <5.7
  8. Affected versionversion=5.7
  9. Affected versionversion=a204d577be70e0a0a6023cf1b9859c9ebffaeecd <b1b31948c0af44628e43353828453461bb74098f
  10. Affected versionversion=a5ce8531ea508d270822b2bc6140c6198c8a2a7b
  11. Affected versionversion=db8bf823e70f239372c62f13e4eb6f08a1665e8c <d624f2991b977821375fbd56c91b0c91d456a697

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=145cb2f7177d94bc54563ed26027e952ee0ae03c <0bfd913c2121b3d553bfd52810fe6061d542d625; version=145cb2f7177d94bc54563ed26027e952ee0ae03c <35b4f24415c854cd718ccdf38dbea6297f010aae; version=145cb2f7177d94bc54563ed26027e952ee0ae03c <61b877bad9bb0d82b7d8841be50872557090a704; version=145cb2f7177d94bc54563ed26027e952ee0ae03c <f01988ecf3654f805282dce2d3bb9afe68d2691e; version=4.19.123 <4.19.191; version=5.4.41 <5.4.120; version=5.6.13 <5.7; version=5.7; version=a204d577be70e0a0a6023cf1b9859c9ebffaeecd <b1b31948c0af44628e43353828453461bb74098f; version=a5ce8531ea508d270822b2bc6140c6198c8a2a7b; version=db8bf823e70f239372c62f13e4eb6f08a1665e8c <d624f2991b977821375fbd56c91b0c91d456a697

Published CVSS scores

9.8kernel.orgCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.8NIST NVDCVSS: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.

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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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
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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