CVE-2026-74583

Memory corruption via stale fastmap pointer republishing

Published Aug 21, 2026 · Updated Aug 25, 2026

Use-after-free in the Linux kernel cls_route classifier allows local users to corrupt memory by racing filter deletion with packet classification. An in-flight route4_classify reader can republish a filter pointer after route4_reset_fastmap clears the cache and schedules that filter for RCU-deferred freeing. Reachability requires concurrent filter changes and classification on the same id and interface tuple; the demonstrated result is a stale-memory read and kernel instability.

CVSS severity7.8
High
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

Use-after-free in the Linux kernel cls_route classifier allows local users to corrupt memory by racing filter deletion with packet classification. An in-flight route4_classify reader can republish a filter pointer after route4_reset_fastmap clears the cache and schedules that filter for RCU-deferred freeing. Reachability requires concurrent filter changes and classification on the same id and interface tuple; the demonstrated result is a stale-memory read and kernel instability.

The record

CVE
CVE-2026-74583
Published
Aug 21, 2026
Updated
Aug 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-825, T1499.004
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Aug 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 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=1109c00547fc66df45b9ff923544be4c1e1bec13 <0e7a8cf8895b06d07c7311f028eba16ad742b9bc
  2. Affected versionversion=1109c00547fc66df45b9ff923544be4c1e1bec13 <47d7f7051253bdc02b1d245d87e38f16d31a74df
  3. Affected versionversion=1109c00547fc66df45b9ff923544be4c1e1bec13 <5ec9001be6d0eb527251125632ec8fe88278897f
  4. Affected versionversion=1109c00547fc66df45b9ff923544be4c1e1bec13 <7897198b26445b4009a057bda1986b94a99e5d5f
  5. Affected versionversion=1109c00547fc66df45b9ff923544be4c1e1bec13 <820f083c294ad6d319c02a7d43294f2ed2565139
  6. Affected versionversion=1109c00547fc66df45b9ff923544be4c1e1bec13 <a17f636c9330eac879822ce29f998e5abd1b72c1
  7. Affected versionversion=1109c00547fc66df45b9ff923544be4c1e1bec13 <ae9aff87025219005a2d16b4fe83d6f24643e50d
  8. Affected versionversion=1109c00547fc66df45b9ff923544be4c1e1bec13 <b969984b2bdc85d721ce4047cd270cd37ec705a2
  9. Affected versionversion=3.18

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=1109c00547fc66df45b9ff923544be4c1e1bec13 <0e7a8cf8895b06d07c7311f028eba16ad742b9bc; version=1109c00547fc66df45b9ff923544be4c1e1bec13 <47d7f7051253bdc02b1d245d87e38f16d31a74df; version=1109c00547fc66df45b9ff923544be4c1e1bec13 <5ec9001be6d0eb527251125632ec8fe88278897f; version=1109c00547fc66df45b9ff923544be4c1e1bec13 <7897198b26445b4009a057bda1986b94a99e5d5f; version=1109c00547fc66df45b9ff923544be4c1e1bec13 <820f083c294ad6d319c02a7d43294f2ed2565139; version=1109c00547fc66df45b9ff923544be4c1e1bec13 <a17f636c9330eac879822ce29f998e5abd1b72c1; version=1109c00547fc66df45b9ff923544be4c1e1bec13 <ae9aff87025219005a2d16b4fe83d6f24643e50d; version=1109c00547fc66df45b9ff923544be4c1e1bec13 <b969984b2bdc85d721ce4047cd270cd37ec705a2; version=3.18

Published CVSS scores

7.8CanonicalCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8Red HatCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8Linux kernel CVE teamCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.0Amazon LinuxCVSS:3.1/AV:L/AC:H/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)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-825Expired Pointer Dereference
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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