CVE-2018-20436 Server-side request forgery in n/a

High 8.1 Published 24 Dec 2018 Updated 5 Aug 2024

Telegram servers send GET requests for URLs typed in secret chats before sending, potentially leaking data or enabling SSRF if link previews are enabled.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2018-20436?

CVE-2018-20436 is a high-severity server-side request forgery vulnerability in n/a, published on 24 Dec 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

The "secret chat" feature in Telegram 4.9.1 for Android has a "side channel" in which Telegram servers send GET requests for URLs typed while composing a chat message, before that chat message is sent. There are also GET requests to other URLs on the same web server. This also affects one or more other Telegram products, such as Telegram Web-version 0.7.0. In addition, it can be interpreted as an SSRF issue. NOTE: a third party has reported that potentially unwanted behavior is caused by misconfiguration of the "Secret chats > Preview links" setting

Weakness: CWE-918

Which versions are affected by CVE-2018-20436?

It affects 2 products.

Products include Telegram Telegram, Telegram Web.

How do I fix CVE-2018-20436?

No fix has been published for CVE-2018-20436 yet. Limit exposure of the affected software until one is available.

Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.

Is CVE-2018-20436 being exploited?

There is no known exploitation of CVE-2018-20436 in the wild and no public exploit code.

Sources

Also known as GHSA-53m8-q7p6-6hq3.