CVE-2023-53821

Slab use-after-free via overlapping skb control fields

Published Dec 9, 2025 · Updated May 11, 2026

Use-after-free in the Linux kernel IPv6 VTI transmit path allows attackers to trigger an invalid kernel memory read during packet transmission. An sfb qdisc writes hash data into the skb control buffer, and decode_session6 later interprets overlapping bytes as a header offset without first clearing that buffer. Exposure requires an affected kernel at or after 3.19 and an IPv6 VTI device using an sfb qdisc; the demonstrated consequence is a KASAN-detected invalid read.

CVSS severityUnavailable
Unscored
EPSS probability0.26%
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 IPv6 VTI transmit path allows attackers to trigger an invalid kernel memory read during packet transmission. An sfb qdisc writes hash data into the skb control buffer, and decode_session6 later interprets overlapping bytes as a header offset without first clearing that buffer. Exposure requires an affected kernel at or after 3.19 and an IPv6 VTI device using an sfb qdisc; the demonstrated consequence is a KASAN-detected invalid read.

The record

CVE
CVE-2023-53821
Published
Dec 9, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Dec 9, 2025CVE publishedPublication date reported by the CVE source.
  2. May 11, 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=3.19
  2. Affected versionversion=f855691975bb06373a98711e4cfe2c224244b536 <0f0ab8d52ee0062b28367dea23c29e254a26d7db
  3. Affected versionversion=f855691975bb06373a98711e4cfe2c224244b536 <55ad2309205cc00c585344374c7472420e1b2c12
  4. Affected versionversion=f855691975bb06373a98711e4cfe2c224244b536 <9fd41f1ba638938c9a1195d09bc6fa3be2712f25
  5. Affected versionversion=f855691975bb06373a98711e4cfe2c224244b536 <a1639a82ce14af76b6419778d343ccbff86ee626
  6. Affected versionversion=f855691975bb06373a98711e4cfe2c224244b536 <c070688bfbe7759e61e697e421b2a331b0dd74bc
  7. Affected versionversion=f855691975bb06373a98711e4cfe2c224244b536 <eb47e612e59c358c3968a92f90dd36c78c9a2106
  8. Affected versionversion=f855691975bb06373a98711e4cfe2c224244b536 <ec23b25e5687dbd644c0f57bcb6af22dd5a6dd36
  9. Affected versionversion=f855691975bb06373a98711e4cfe2c224244b536 <fa6c6c04f6c9b21b315023f487e5a07ae7fcf647

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=3.19; version=f855691975bb06373a98711e4cfe2c224244b536 <0f0ab8d52ee0062b28367dea23c29e254a26d7db; version=f855691975bb06373a98711e4cfe2c224244b536 <55ad2309205cc00c585344374c7472420e1b2c12; version=f855691975bb06373a98711e4cfe2c224244b536 <9fd41f1ba638938c9a1195d09bc6fa3be2712f25; version=f855691975bb06373a98711e4cfe2c224244b536 <a1639a82ce14af76b6419778d343ccbff86ee626; version=f855691975bb06373a98711e4cfe2c224244b536 <c070688bfbe7759e61e697e421b2a331b0dd74bc; version=f855691975bb06373a98711e4cfe2c224244b536 <eb47e612e59c358c3968a92f90dd36c78c9a2106; version=f855691975bb06373a98711e4cfe2c224244b536 <ec23b25e5687dbd644c0f57bcb6af22dd5a6dd36; version=f855691975bb06373a98711e4cfe2c224244b536 <fa6c6c04f6c9b21b315023f487e5a07ae7fcf647

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

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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