BugZero | F5 BugID 1056401 - Valid clients connecting under active syncookie mo...

F5 - Defect ID: 1056401

Valid clients connecting under active syncookie mode might experience latency.

F5 - Defect ID: 1056401

Valid clients connecting under active syncookie mode might experience latency.

Last updated on July 18th, 2026

BugZero Risk Score
6.9 Medium

Overall: 6.9

Severity: 7.3

Community: 4.2

Lifecycle: 8.3

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Bug Details

Priority: 3-Major
Status: Verified
Impact Category: Local Traffic Manager

Description

Symptoms

Valid clients that connect using active syncookie mode might experience latency.

Impact

Random connections might be disrupted.

Conditions

- SYN Cookie (Hardware or Software) is enabled. - SYN Cookies are activated (TCP Half Open) for the virtual server. - FastL4 tcp-generate-isn option or SYN-ACK vector 'suspicious event count' options are enabled. - SYN Cookie issue and validation with client is correct. - SSL Client Hello packet sent by client reaches DHD right after TCP SYN packet is sent to backend server.

Workaround

None

Fix Information

None

Change history

Links

Original Vendor Announcement

Relevant Products

Click on a version to see all relevant bugs

Affected versions:13.1.0, 13.1.0.1, 13.1.0.2, 13.1.0.3, 13.1.0.4, 13.1.0.5, 13.1.0.6, 13.1.0.7, 13.1.0.8, 13.1.1, 13.1.1.2, 13.1.1.3, 13.1.1.4, 13.1.1.5, 13.1.3, 13.1.3.1, 13.1.3.2, 13.1.3.3, 13.1.3.4, 13.1.3.5, 13.1.3.6, 13.1.4, 13.1.4.1, 13.1.5, 13.1.5.1, 14.1.0, 14.1.0.1, 14.1.0.2, 14.1.0.3, 14.1.0.5, 14.1.0.6, 14.1.2, 14.1.2.1, 14.1.2.2, 14.1.2.3, 14.1.2.4, 14.1.2.5, 14.1.2.6, 14.1.2.7, 14.1.2.8, 14.1.3, 14.1.3.1, 14.1.4, 14.1.4.1, 14.1.4.2, 14.1.4.3, 14.1.4.4, 14.1.4.5, 14.1.4.6, 14.1.5, 14.1.5.1, 14.1.5.2, 14.1.5.3, 14.1.5.4, 14.1.5.6, 15.1.0, 15.1.0.1, 15.1.0.2, 15.1.0.3, 15.1.0.4, 15.1.0.5, 15.1.1, 15.1.2, 15.1.2.1, 15.1.3, 15.1.3.1, 15.1.4, 15.1.4.1, 15.1.5, 16.1.0, 16.1.1, 16.1.2, 16.1.2.1

Fixed versions: 17.0.0, 16.1.2.2, 15.1.5.1

Relevant Products

Click on a version to see all relevant bugs

Fixed versions: 17.0.0, 16.1.2.2, 15.1.5.1

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F5 - Defect ID: 1056401

Valid clients connecting under active syncookie mode might experience latency.

F5 - Defect ID: 1056401

Valid clients connecting under active syncookie mode might experience latency.

Last updated on July 18th, 2026

BugZero Risk Score6.9 Medium

Bug Details

Symptoms

Impact

Conditions

Workaround

Fix Information

Links

Top F5 Defects

Ready to prevent the next vendor outage?

F5 - Defect ID: 1056401

Valid clients connecting under active syncookie mode might experience latency.

F5 - Defect ID: 1056401

Valid clients connecting under active syncookie mode might experience latency.

Last updated on July 18th, 2026

BugZero Risk Score6.9 Medium

Bug Details

Symptoms

Impact

Conditions

Workaround

Fix Information

Links

Top F5 Defects

Ready to prevent the next vendor outage?

BugZero Risk Score
6.9 Medium

BugZero Risk Score
6.9 Medium