> Source: [sk164775](https://support.checkpoint.com/results/sk/sk164775)

# sk164775 - Predictable TCP sequences generated by Security Gateway in R80.20 / R80.30

| Property | Value |
|----------|-------|
| Solution ID | sk164775 |
| Date Created | 2020-01-23 |
| Last Modified | 2020-02-18 |
| Technical Level | General |
| Products | Security Gateway |
| Versions | R82.10, R82, R81.20 |

## Symptoms

- Predictable TCP sequences are generated by the Security Gateway.

## Cause

Since R80.20, predictable TCP sequences are generated (in some cases) by the Security Gateway as a result of a functionality bug.

This might happen when using the following blades/protections (for example):

* HTTPS Inspection for HTTPS connections
* 'Header spoofing' IPS protection
* User web portals on Security Gateway

Since in most of the cases these types of connections are encrypted, an attacker could use it only to create spoof reset, **not** session hijack.

If successful, it could cause disconnections of specific connection.

## Solution

This problem was fixed. The fix is included in:

* **[Jumbo Hotfix Accumulator for R80.30](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk153152) (since Take_135)**
* **[Jumbo Hotfix Accumulator for R80.20](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk137592) (since Take_134)**

Check Point recommends to always [upgrade to the most recent version](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doShowproductpage&productTab=overview&product=435).  

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