Telegram rlottie 7.0.1_2065 LottieParserImpl::parseDashProperty Heap Buffer Overflow


Telegram rlottie 7.0.1_2065 is affected by a Heap Buffer Overflow in the LottieParserImpl::parseDashProperty function: a remote attacker might be able to access heap memory out-of-bounds on a victim device. Note: we’ll walk through the android app sources, but the issue applies to iOS and macOS Telegram apps too.

Product Description (from vendor)

“Telegram is a cloud-based mobile and desktop messaging app with a focus on security and speed.”. For more information visit



Root Cause Analysis

Telegram uses a custom fork of rlottie to render animated stickers. The vulnerability is a heap-based buffer overflow which originates in LottieParserImpl::parseDashProperty (starting at ): an out-of-bounds read access is performed because the actual number of dashes in the animated sticker is not verified before acessing heap memory.

The number of dashes in a GradientStroke shape is five ( ). In case there are more dashes, out-of-bounds memory is accessed in

Proof of Concept

A blogpost will be published soon on our blog with a PoC walkthrough and further details.


A remote attacker might be able to access Telegram’s heap memory out-of-bounds on a victim device.


Upgrade to Telegram 7.1.0 (2090) or later.

Disclosure Timeline

  • 30/09/2020:
    • Telegram releases version 7.1.0 (2090) with a patch


`polict` of Shielder

This advisory was first published on


16 febbraio 2021