CVE-2026-45840

Kernel panic via unbounded upcall PID array

Published May 27, 2026 · Updated May 27, 2026

Denial of service in the Linux Kernel allows local users to panic the kernel via an oversized Open vSwitch upcall PID array. ovs_vport_set_upcall_portids() accepts an unbounded PID array, while reply helpers serialize it into a fixed-size skb and BUG_ON the resulting nla_put() failure. Reachability requires CAP_NET_ADMIN, although unprivileged user namespaces can grant that capability inside a new namespace; triggering the flaw can crash or panic the host kernel.

CVSS severity5.5
Medium
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

Denial of service in the Linux Kernel allows local users to panic the kernel via an oversized Open vSwitch upcall PID array. ovs_vport_set_upcall_portids() accepts an unbounded PID array, while reply helpers serialize it into a fixed-size skb and BUG_ON the resulting nla_put() failure. Reachability requires CAP_NET_ADMIN, although unprivileged user namespaces can grant that capability inside a new namespace; triggering the flaw can crash or panic the host kernel.

The record

CVE
CVE-2026-45840
Published
May 27, 2026
Updated
May 27, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 27, 2026CVE publishedPublication date reported by the CVE source.
  2. May 27, 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=3.17
  2. Affected versionversion=5cd667b0a4567048bb555927d6ee564f4e5620a9 <1d6c02b86329883aa467a3a61f8d34369db73a2f
  3. Affected versionversion=5cd667b0a4567048bb555927d6ee564f4e5620a9 <2091c6aa0df6aba47deb5c8ab232b1cb60af3519
  4. Affected versionversion=5cd667b0a4567048bb555927d6ee564f4e5620a9 <f99ac36b5d7c719d08a69fcdecce40f78a874e15
  5. Affected versionversion=5cd667b0a4567048bb555927d6ee564f4e5620a9 <f9ef3db77a383d66847fd082c2b437d8ae4d9c63
  6. Affected versionversion=5cd667b0a4567048bb555927d6ee564f4e5620a9 <fa6e90bc443bed8dc0d55bc5ea5b27ffdfe37704

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=3.17; version=5cd667b0a4567048bb555927d6ee564f4e5620a9 <1d6c02b86329883aa467a3a61f8d34369db73a2f; version=5cd667b0a4567048bb555927d6ee564f4e5620a9 <2091c6aa0df6aba47deb5c8ab232b1cb60af3519; version=5cd667b0a4567048bb555927d6ee564f4e5620a9 <f99ac36b5d7c719d08a69fcdecce40f78a874e15; version=5cd667b0a4567048bb555927d6ee564f4e5620a9 <f9ef3db77a383d66847fd082c2b437d8ae4d9c63; version=5cd667b0a4567048bb555927d6ee564f4e5620a9 <fa6e90bc443bed8dc0d55bc5ea5b27ffdfe37704

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5Canonical UbuntuCVSS: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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

T1499.004Endpoint Denial of Service: Application 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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