CVE-2026-98794
Received Received - Intake

IPVS SYNC Protocol Message Filtering in Linux Kernel

Publication date: 2026-10-18

Last updated on: 2026-10-18

Assigner: kernel.org

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.

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Meta Information

Published
2026-10-18
Last Modified
2026-10-18
Generated
2026-10-18
AI Q&A
2026-10-18
EPSS Evaluated
N/A
NVD
CVE-2026-98794
EUVD
EUVD-2026-103879

Affected Vendors & Products

Showing 5 associated CPEs
Vendor Product Version / Range
Linux Linux 87375ab47cd0ba04124c6d3fd80db5c368f5dcb6
Linux Linux 87375ab47cd0ba04124c6d3fd80db5c368f5dcb6
Linux Linux 87375ab47cd0ba04124c6d3fd80db5c368f5dcb6
Linux Linux 87375ab47cd0ba04124c6d3fd80db5c368f5dcb6
Linux Linux 2.6.14

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves improper handling of flags received in the backup server for the IPVS SYNC protocol. The issue allows certain flag combinations, like NO_CPORT+TEMPLATE, to cause incorrect connection lookups or template breaks. Additionally, the ONE_PACKET flag, which should not be sent by the master, could create unhashed connections in the backup server.

Impact Analysis

If exploited, this vulnerability could allow an attacker to disrupt load balancing or cause denial-of-service conditions by sending malformed messages to the backup server. It may lead to incorrect connection handling, system instability, or unexpected behavior in the IPVS (IP Virtual Server) functionality.

Mitigation Strategies

Update the Linux kernel to a patched version that includes the fix for CVE-2026-98794. Monitor kernel security advisories for the specific kernel version that resolves this issue.

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