CVE-2026-53236

TCP metadata disclosure via unprivileged socket filters

Published Jun 25, 2026 · Updated Jun 25, 2026

Information disclosure in the Linux kernel allows local users to leak TCP sequence and acknowledgment numbers through a socket filter. The TCP socket filter attachment path in net/core/sock.c accepted SO_ATTACH_FILTER classic BPF programs from callers without CAP_NET_ADMIN, exposing TCP connection metadata to the attached filter. A local low-privileged process must create a TCP socket and attach the filter; the bounded consequence is indirect disclosure of sequence and acknowledgment metadata.

CVSS severity5.5
Medium
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in the Linux kernel allows local users to leak TCP sequence and acknowledgment numbers through a socket filter. The TCP socket filter attachment path in net/core/sock.c accepted SO_ATTACH_FILTER classic BPF programs from callers without CAP_NET_ADMIN, exposing TCP connection metadata to the attached filter. A local low-privileged process must create a TCP socket and attach the filter; the bounded consequence is indirect disclosure of sequence and acknowledgment metadata.

The record

CVE
CVE-2026-53236
Published
Jun 25, 2026
Updated
Jun 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1040
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 25, 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=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <3747de241a66ef2c7032d2cc2b826a47c5fa0f6a
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <5d39580f68e6ddeedd15e587282207489dfb3da2
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <82b3e7ce10c53fc12aab8904745603efc74f8c07
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c68517a3e18e20997808821c5559d0cba4d776c1
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ecfe9171b26ae3eed0cd8bab7a943e9e2c9e51ba
  6. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ede69b8f6670600e534591664584f810d7c385f9
  7. Affected versionversion=2.6.12

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <3747de241a66ef2c7032d2cc2b826a47c5fa0f6a; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <5d39580f68e6ddeedd15e587282207489dfb3da2; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <82b3e7ce10c53fc12aab8904745603efc74f8c07; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c68517a3e18e20997808821c5559d0cba4d776c1; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ecfe9171b26ae3eed0cd8bab7a943e9e2c9e51ba; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ede69b8f6670600e534591664584f810d7c385f9; version=2.6.12

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

T1040Network Sniffing

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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