AI-Assisted 'WeWorm' Zero-Click Worm Spreads via WeChat Calls on iOS and Android; Patched in Android 8.0.77 and iOS 8.0.76

California researchers used LLMs to find a memory-corruption RCE in WeChat's VoIP stack and build WeWorm, described as the first zero-click worm spreading through WeChat calls on iOS and Android; Tencent patched the flaw in WeChat Android 8.0.77 and iOS…

Researchers in California discovered a memory-corruption flaw in WeChat's VoIP stack in July with the help of open-weight and frontier LLMs, produced a working remote-code-execution exploit in about two days, and then spent one more week building WeWorm — which they describe as the first zero-click worm to spread through WeChat calls on both iOS and Android. A crafted incoming call triggers code execution with no user interaction: the exploit succeeds even if the victim never answers, and victims hear nothing even if they do. It gives the attacker full control of the victim's WeChat account; the attacker only needs to be on the victim's friend list, which is easily achieved by compromising a trusted contact first, after which the worm spreads by calling that contact's friends. The team argues AI can now do most exploit-development work — effort that previously took larger teams months — with humans supplying judgment on targeting and safe testing; WeWorm was released as a demo and tested on test phones. Tencent confirmed the bug and shipped patches in WeChat Android 8.0.77 and iOS 8.0.76. No in-the-wild exploitation has been reported, and the researchers note that chaining the flaw with other OS bugs could yield full device control.

• WeWorm is described by its creators as the first zero-click worm spreading through WeChat calls, affecting both iOS and Android
• Underlying vulnerability: a memory-corruption RCE in WeChat's VoIP stack, discovered in July using open-weight and frontier LLMs
• AI helped find the bug and write the RCE exploit in about two days; building the worm took one additional week
• The exploit requires no user interaction and works even if the victim never answers; victims hear nothing even if they answer
• The attacker only needs to be on the victim's WeChat friend list, achieved by compromising a trusted contact first; the worm then spreads by calling the contacts' friends
• Compromise gives full control of the victim's WeChat account; chaining with other OS bugs could yield full device control
• Tencent confirmed the bug and shipped patches in WeChat Android 8.0.77 and iOS 8.0.76
• No in-the-wild exploitation reported; the worm was tested on test phones and released as a demo