Telegram rlottie 7.0.1_2065 is affected by a Stack Based Overflow in the blit function: a remote attacker might be able to access Telegram’s stack 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.
“Telegram is a cloud-based mobile and desktop messaging app with a focus on security and speed.”. For more information visit https://telegram.org/.
Telegram uses a custom fork of rlottie to render animated stickers. A malicious animated sticker with multiple “maskProperties” might bypass the protection in place against out-of-bounds access during the rendering process. The bound checks in place are not sufficient against a negative index: the resulting offset might point to memory before the target region
buffer in https://github.com/DrKLO/Telegram/blob/release-7.0.1_2065/TMessagesProj/jni/rlottie/src/vector/vrle.cpp#L562:
spans->x is negative, an out-of-bounds read access is triggered. The read access violation happens shortly later inside the
std::max call at https://github.com/DrKLO/Telegram/blob/release-7.0.1_2065/TMessagesProj/jni/rlottie/src/vector/vrle.cpp#L569:
where the address of
ptr is calculated using the negative
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 stack memory out-of-bounds on a victim device.
Upgrade to Telegram 7.1.0 (2090) or later.
`polict` of Shielder
This advisory was first published on https://www.shielder.com/advisories/telegram-rlottie-blit-stack-buffer-overflow/
16 February 2021