Session Fixation in admidio/admidio


Reported on

Dec 8th 2021


Session Fixation is an attack that permits an attacker to hijack a valid user session. The attack explores a limitation in the way the web application manages the session ID, more specifically the vulnerable web application. When authenticating a user, it doesn't assign a new session ID, making it possible to use an existent session ID.

Proof of Concept

1. Load website in a new browser
2. Get cookie before login
3. Login to the website
4. Get cookie after login
Compare those 2 values

Before login, ADMIDIO_DEMO_d00c3e23_demo_en_SESSION_ID=fixation
The login HTTP response contains Set-cookie response to set a new cookie but that cookie is the same as one before login.
After logging in, the session is still with cookie ADMIDIO_DEMO_d00c3e23_demo_en_SESSION_ID=fixation


The attack consists of inducing a user to authenticate himself with a known session ID and then hijacking the user-validated session by the knowledge of the used session ID. The attacker has to provide a legitimate Web application session ID and try to make the victim's browser use it.


Web applications must ignore any session ID provided by the user's browser at login and must always generate a new session to which the user will log in if successfully authenticated.

We are processing your report and will contact the admidio team within 24 hours. 2 years ago
We have contacted a member of the admidio team and are waiting to hear back 2 years ago
We have sent a follow up to the admidio team. We will try again in 7 days. 2 years ago
Markus Faßbender validated this vulnerability 2 years ago
KhanhCM has been awarded the disclosure bounty
The fix bounty is now up for grabs
Markus Faßbender marked this as fixed in 4.1 with commit c5dfae 2 years ago
Markus Faßbender has been awarded the fix bounty
This vulnerability will not receive a CVE
login_check.php#L21-L40 has been validated
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