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

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

- **Severity:** High 8.1 (`CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Dec 2018
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-53m8-q7p6-6hq3

## 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 (Server-Side Request Forgery)

## Which versions are affected by CVE-2018-20436?

It affects 2 products.


Products: 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.

## Is CVE-2018-20436 being exploited?

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

## Other vulnerabilities in n/a

- [CVE-2019-10044](https://insights.sbomify.com/CVE-2019-10044/): Other in n/a (high 8.8)
- [CVE-2024-7014](https://insights.sbomify.com/CVE-2024-7014/): Improper multimedia file attachment validation in Telegram for Android app (high 7.1)
- [CVE-2021-31320](https://insights.sbomify.com/CVE-2021-31320/): Memory corruption in n/a (high 7.1)
- [CVE-2021-31321](https://insights.sbomify.com/CVE-2021-31321/): Memory corruption in n/a (high 7.1)
- [CVE-2018-15543](https://insights.sbomify.com/CVE-2018-15543/): Auth bypass in n/a (medium 6.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-20436 and fix it if it is affected.

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

Affected product: n/a. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2018-20436/ (Markdown: https://insights.sbomify.com/CVE-2018-20436/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-20436
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-20436
- OSV: https://osv.dev/vulnerability/CVE-2018-20436

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-20436/
Summaries are generated and may contain mistakes; the official description above is the record.