CVE-2021-44538

The olm_session_describe function in Matrix libolm before 3.2.7 is vulnerable to a buffer overflow. The Olm session object represents a cryptographic channel between two parties. Therefore, its state is partially controllable by the remote party of the channel. Attackers can construct a crafted sequence of messages to manipulate the state of the receiver's session in such a way that, for some buffer sizes, a buffer overflow happens on a call to olm_session_describe. Furthermore, safe buffer sizes were undocumented. The overflow content is partially controllable by the attacker and limited to ASCII spaces and digits. The known affected products are Element Web And SchildiChat Web.

• Cinny Project Cinny

  APP
  Cinny Project
  < 1.6.0

• Debian

  OS
  Debian
  10.011.09.0

• Matrix Element

  APP
  Matrix
  < 1.9.7

• Matrix Javascript Sdk

  APP
  Matrix
  2.4.2 – 15.2.1 (bez)

• Matrix Olm

  APP
  Matrix
  3.1.4 – 3.2.8 (bez)

• Schildi Schildichat

  APP
  Schildi
  < 1.9.7-sc1