CVE-2026-74478Network attack vector

Guest crash via stale freed receive slot

Published Aug 15, 2026 · Updated Aug 15, 2026

Use-after-free in Linux User Mode Linux vector networking allows remote attackers to crash a guest via crafted GRE or L2TPv3 packets. The vector_mmsg_rx() rejection path frees an skb but leaves its slot and cursors unchanged, causing the next loop iteration to free the same buffer again. Any unauthenticated peer on a configured GRE or L2TPv3 vector transport can cause the refcount underflow; raw and tap transports are not affected.

CVSS severity9.8
Critical
EPSS probability0.57%
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 Linux User Mode Linux vector networking allows remote attackers to crash a guest via crafted GRE or L2TPv3 packets. The vector_mmsg_rx() rejection path frees an skb but leaves its slot and cursors unchanged, causing the next loop iteration to free the same buffer again. Any unauthenticated peer on a configured GRE or L2TPv3 vector transport can cause the refcount underflow; raw and tap transports are not affected.

The record

CVE
CVE-2026-74478
Published
Aug 15, 2026
Updated
Aug 15, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, CWE-763, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 15, 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=4.17
  2. Affected versionversion=49da7e64f33e80edffb1a9eeb230fa4c3f42dffb <180ff4c81faf01ec4e06082c9daa7c40518ead89
  3. Affected versionversion=49da7e64f33e80edffb1a9eeb230fa4c3f42dffb <4b9601595e8b6b5d18878cac0aeabc687d241111
  4. Affected versionversion=49da7e64f33e80edffb1a9eeb230fa4c3f42dffb <67d58ab4f2ccf7145f3da07e025735a09c79de1b
  5. Affected versionversion=49da7e64f33e80edffb1a9eeb230fa4c3f42dffb <804b681002ead233abf49a3efd681f5468a835f9
  6. Affected versionversion=49da7e64f33e80edffb1a9eeb230fa4c3f42dffb <af421e9aed3920c7ac88c24daa48606c7112feca

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.17; version=49da7e64f33e80edffb1a9eeb230fa4c3f42dffb <180ff4c81faf01ec4e06082c9daa7c40518ead89; version=49da7e64f33e80edffb1a9eeb230fa4c3f42dffb <4b9601595e8b6b5d18878cac0aeabc687d241111; version=49da7e64f33e80edffb1a9eeb230fa4c3f42dffb <67d58ab4f2ccf7145f3da07e025735a09c79de1b; version=49da7e64f33e80edffb1a9eeb230fa4c3f42dffb <804b681002ead233abf49a3efd681f5468a835f9; version=49da7e64f33e80edffb1a9eeb230fa4c3f42dffb <af421e9aed3920c7ac88c24daa48606c7112feca

Published CVSS scores

9.8Linux CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
8.2Amazon LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
5.5Red HatCVSS: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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
CWE-763Release of Invalid Pointer or Reference
T1499Endpoint Denial of Service

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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