CVE-2026-64422

Kernel-memory disclosure and crash via MTU probing

Published Jul 25, 2026 · Updated Jul 25, 2026

Affected Linux Kernel releases allow local users to disclose kernel memory or crash the system through crafted TCP MTU probing. A negative net.ipv4.tcp_reordering value wraps when copied from int to u32, then overflows tcp_mtu_probe() size arithmetic and bypasses send-queue checks. Exploitation requires CAP_NET_ADMIN in a network namespace, tcp_mtu_probing=2, and an attacker-controlled TCP connection; remote packets alone cannot trigger the flaw.

CVSS severity7.1
High
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Affected Linux Kernel releases allow local users to disclose kernel memory or crash the system through crafted TCP MTU probing. A negative net.ipv4.tcp_reordering value wraps when copied from int to u32, then overflows tcp_mtu_probe() size arithmetic and bypasses send-queue checks. Exploitation requires CAP_NET_ADMIN in a network namespace, tcp_mtu_probing=2, and an attacker-controlled TCP connection; remote packets alone cannot trigger the flaw.

The record

CVE
CVE-2026-64422
Published
Jul 25, 2026
Updated
Jul 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 25, 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=2.6.24
  2. Affected versionversion=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <27ddf4486c7dbf5bdd393fa8bef6b67179796d98
  3. Affected versionversion=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <782708ca1ea1f68b8cbb5ea3a7f5f18d0000efae
  4. Affected versionversion=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <99206ce2244f8a3ed64298d0667c9055845a5dc7
  5. Affected versionversion=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <a094ac95d3b69adfa1676eb9c8eae6835d4f1671
  6. Affected versionversion=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <bbae351c0f32f7c200249e4aa6561b2b419dcf69
  7. Affected versionversion=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <e81f805824a8109504fce090641b17d135b48cd1
  8. Affected versionversion=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <efb8763d7bbb40cff4cc55a6b62c3095a038149c
  9. Affected versionversion=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <f0d88a4cd03affff6c08adf6c63964e235aede43

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=2.6.24; version=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <27ddf4486c7dbf5bdd393fa8bef6b67179796d98; version=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <782708ca1ea1f68b8cbb5ea3a7f5f18d0000efae; version=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <99206ce2244f8a3ed64298d0667c9055845a5dc7; version=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <a094ac95d3b69adfa1676eb9c8eae6835d4f1671; version=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <bbae351c0f32f7c200249e4aa6561b2b419dcf69; version=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <e81f805824a8109504fce090641b17d135b48cd1; version=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <efb8763d7bbb40cff4cc55a6b62c3095a038149c; version=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <f0d88a4cd03affff6c08adf6c63964e235aede43

Published CVSS scores

7.1kernel.orgCVSS: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

T1499.004Application or System Exploitation

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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