CVE-2024-26677

Invalid RTT reference via delayed-ACK serial copy

Published Apr 2, 2024 · Updated May 11, 2026

Improper delayed-ACK construction in the Linux kernel's RxRPC subsystem causes packets to carry an unusable RTT reference serial. The ACK builder copies the triggering DATA packet's serial into RX_ACK_DELAY packets even though RxRPC implementations exclude that ACK reason from RTT estimation. Upstream participants characterize the change as a performance optimization rather than a security fix, and no attacker-controlled path is established.

CVSS severity5.5
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper delayed-ACK construction in the Linux kernel's RxRPC subsystem causes packets to carry an unusable RTT reference serial. The ACK builder copies the triggering DATA packet's serial into RX_ACK_DELAY packets even though RxRPC implementations exclude that ACK reason from RTT estimation. Upstream participants characterize the change as a performance optimization rather than a security fix, and no attacker-controlled path is established.

The record

CVE
CVE-2024-26677
Published
Apr 2, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 2, 2024CVE 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=17926a79320afa9b95df6b977b40cca6d8713cea <200cb50b9e154434470c8969d32474d38475acc2
  2. Affected versionversion=17926a79320afa9b95df6b977b40cca6d8713cea <63719f490e6a89896e9a463d2b45e8203eab23ae
  3. Affected versionversion=17926a79320afa9b95df6b977b40cca6d8713cea <e7870cf13d20f56bfc19f9c3e89707c69cf104ef
  4. Affected versionversion=2.6.22

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=17926a79320afa9b95df6b977b40cca6d8713cea <200cb50b9e154434470c8969d32474d38475acc2; version=17926a79320afa9b95df6b977b40cca6d8713cea <63719f490e6a89896e9a463d2b45e8203eab23ae; version=17926a79320afa9b95df6b977b40cca6d8713cea <e7870cf13d20f56bfc19f9c3e89707c69cf104ef; version=2.6.22

Published CVSS scores

5.5NIST National Vulnerability DatabaseCVSS: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

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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