Security Experts:

Zero-Day Attack Prompts Emergency Patch for Bitmessage Client

An emergency update released on Tuesday for the PyBitmessage application patches a critical remote code execution vulnerability that has been exploited in attacks.

Bitmessage is a decentralized and trustless communications protocol that can be used for sending encrypted messages to one or multiple users. PyBitmessage is the official client for Bitmessage.

Bitmessage developers have issued a warning for a zero-day flaw that has been exploited against some users running PyBitmessage 0.6.2.

The security hole, described as a message encoding bug, has been patched with the release of version 0.6.3.2, but since PyBitmessage 0.6.1 is not affected by the flaw, downgrading is also an option for mitigating potential attacks.

Code patches were released on Tuesday, and binary files for Windows and macOS are expected to become available on Wednesday.

One of the individuals targeted in the zero-day attacks was Bitmessage core developer Peter Šurda. The developer told users not to contact him on his old address and admitted that his keys were most likely compromised. A new support address has been added to PyBitmessage 0.6.3.2.

“If you have a suspicion that your computer was compromised, please change all your passwords and create new bitmessage keys,” Surda said.

According to Šurda, the attacker exploited the vulnerability in an effort to create a remote shell and steal bitcoins from Electrum wallets.

“The exploit is triggered by a malicious message if you're the recipient (including joined chans),” the developer explained. “The attacker ran an automated script but also opened, or tried to open, a remote reverse shell. The automated script looked in ~/.electrum/wallets, but when using the reverse shell he had access to other files as well.”

The investigation into these attacks is ongoing and Bitmessage developers have promised to share more information as it becomes available.

Bitmessage has become increasingly popular in the past years following reports that the U.S. National Security Agency and other intelligence agencies are conducting mass surveillance. While the protocol is often used by people looking to protect their privacy, it has also been leveraged by cybercriminals, including in ransomware attacks for communications between victims and the hackers.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.