CVE-2026-98794

ipvs: filter some flags received in the backup server

Published Oct 18, 2026 CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

ipvs: filter some flags received in the backup server

While the IPVS SYNC protocol is not secure by design
we can still protect the backup server from messages that
can wreak havoc.

This commit addresses problems from received connection flags
or their combinations. We now drop messages as follows:

1. the NO_CPORT+TEMPLATE combination allows lookups for normal
connections to hit template which can break in many ways.
While the master does not sync connections with NO_CPORT flag,
i.e. before they are established, we still accept NO_CPORT
without TEMPLATE.

2. ONE_PACKET: it is not sent by master, so we do not
expect it in backup. Before now it was ignored by
IP_VS_CONN_F_BACKUP_MASK for protocol v1 while protocol
v0 created connections that are not hashed and dropped
immediately. Better to apply the IP_VS_CONN_F_BACKUP_MASK
also to the flags from v0 messages for consistency with v1.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4850-1 linux-6.12 security update
Ubuntu USN Ubuntu USN USN-9018-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9018-2 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-9019-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9020-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9022-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9023-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9024-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9025-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9026-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9039-1 Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-9040-1 Linux kernel (Low Latency NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9066-1 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-9091-1 Linux kernel (NVIDIA Tegra) vulnerabilities
History
Type Values Removed Values Added
Weaknesses CWE-20
Type Values Removed Values Added
Weaknesses CWE-1288
References
Metrics threat_severity

None

cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate

Type Values Removed Values Added
Weaknesses CWE-20
Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: ipvs: filter some flags received in the backup server While the IPVS SYNC protocol is not secure by design we can still protect the backup server from messages that can wreak havoc. This commit addresses problems from received connection flags or their combinations. We now drop messages as follows: 1. the NO_CPORT+TEMPLATE combination allows lookups for normal connections to hit template which can break in many ways. While the master does not sync connections with NO_CPORT flag, i.e. before they are established, we still accept NO_CPORT without TEMPLATE. 2. ONE_PACKET: it is not sent by master, so we do not expect it in backup. Before now it was ignored by IP_VS_CONN_F_BACKUP_MASK for protocol v1 while protocol v0 created connections that are not hashed and dropped immediately. Better to apply the IP_VS_CONN_F_BACKUP_MASK also to the flags from v0 messages for consistency with v1.
Title ipvs: filter some flags received in the backup server
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Oct 30, 2026, 12:39 PM
Reserved
Sep 25, 2026, 10:25 AM
Status
Received
Published
Oct 18, 2026, 4:17 PM
Modified
Oct 30, 2026, 1:21 PM
Severity
Moderate
Public date
Oct 18, 2026, 12:00 AM