According to Israeli cybersecurity firm A Security, a researcher used fewer than 20 AI prompts with publicly available artificial intelligence models to uncover three Zoom vulnerabilities and build a working attack in less than 24 hours. The firm named the attack 'Zoomsday' and said the vulnerabilities affected Zoom's annotation system, which lets meeting participants draw or add notes to shared content. The discovered vulnerabilities are tracked as CVE-2026-53413, CVE-2026-53414 and CVE-2026-53415 and were tested against Zoom applications running on Windows, macOS, Linux, Android and iOS. As per A Security, the AI agent mapped the attack surface, reverse-engineered the closed-source annotation protocol, identified the memory corruption vulnerability, built the exploit payload, and achieved confirmed remote code execution on a live victim, all using publicly available frontier models in a single working day.
Once exploited, the flaws could allow malicious code to run on another participant's device without requiring the person to download a file, click a link, or approve an action. According to A Security, the attacker could then steal personal information, install malware, or activate a device's microphone and camera. The attack could work from either side of a call, with a compromised presenter attacking participants or a participant targeting the presenter. An attacker only needed to join or host the meeting before sending the malicious data required to trigger the vulnerability, with no further interaction required from the target. The vulnerability exploited Zoom's annotation feature, where annotation runs on a proprietary protocol with no public documentation, and every Zoom client automatically parses whatever it receives through this channel without validating the sender's role or message type.
The core bug was a memory-corruption flaw tracked as CVE-2026-53413 with a critical CVSS 4.0 score of 9.0. The annotation protocol's text deserializer reads four fixed 128-byte buffers using a 32-bit character count supplied directly from the wire, with no bounds check comparing the count against the buffer's actual capacity. An oversized count writes past the buffer's boundary into the function's stack frame, overwriting saved registers and the return address with attacker-controlled bytes. A companion over-read vulnerability (CVE-2026-53414) leaked live heap contents including code pointers and vtable addresses, providing the ASLR bypass material an attacker needs to target the overflow precisely. A third independent vulnerability (CVE-2026-53415) involved a separate message type that read attacker-supplied bytes directly into an internal linked-list structure and then unlinked it without validating the pointers, creating a write-what-where primitive offering another path to remote code execution.
The vulnerabilities pose particular risks to cryptocurrency users because attackers have previously used compromised Zoom meetings to steal wallet data and other sensitive information. In January, hackers were using compromised Telegram accounts and deepfake Zoom calls to target cryptocurrency professionals, with attackers impersonating known contacts before using apparent audio problems to convince victims to install malware. In September 2025, THORChain co-founder JP Thor lost about ₹10.7 crore after a compromised Telegram account was used to draw him into what appeared to be a legitimate Zoom meeting. Similar attacks have resulted in cryptocurrency theft, with a December 2025 report detailing a $300 million campaign where North Korean hackers allegedly hijacked trusted Telegram accounts and used fake Zoom meetings to target cryptocurrency executives.
According to A Security, the firm reported the first Zoom vulnerability on June 10 and worked through the disclosure process while fixes were prepared. Zoom responded quickly, deploying a client-side fix in version 7.1.0 by June 22 and a server-side mitigation on July 15 that filters malicious annotation messages before they reach clients. However, the server-side protection does not cover end-to-end encrypted meetings because the server cannot inspect content it cannot decrypt. Organizations using Zoom E2EE with clients older than 7.1.5 remain exposed and should update immediately. The company separately advises users to run the latest versions of its software to receive current security fixes and improvements.
