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PYSEC-2026-555

CriticalCVSS 9.1 / 10

Published Jun 29, 2026·Last modified Jun 29, 2026

Affected Components(0)

No affected components available

Description

Impact

Websites that use Website.user_vars property in versions.

Patches

It affects versions v2.0.1 to v2.4.0. Please upgrade to v2.4.1

Workarounds

Do not use Website.user_vars in websites when using versions v2.0.1 to v2.4.0. Also, do not use Website.signin_user() in version v2.4.0 only.

Explanation

ToUI is using Flask-Caching (SimpleCache) to store user variables. My misunderstanding was that these caches are stored in the client's browser, but it seems that these are stored in the server side.

Risk Scores

Base Score

9.1

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data.

Threat Intelligence

8.3

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS

0.65%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit

Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Critical severity

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