A critical software vulnerability discovered in privacy-focused communication platforms can inadvertently keep user hardware active long after a call has ostensibly ended. According to reports and technical disclosures, a flaw residing within Signal’s underlying communication library allows audio and potentially video streams to persist if a malicious remote peer manipulates the application's event handling during termination. Users who rely on encryption and trusted UI controls face a subtle breakdown in hardware isolation, highlighting ongoing challenges in real-time protocol security.
Understanding the RingRTC Event Queue Flaw
At the core of the issue is how Signal manages call states through its RingRTC library, specifically in versions prior to 2.72.0. Technical analysis reveals that a local hang-up request does not act as an immediate hardware kill switch. Instead, the command is treated as a standard event placed at the back of a finite-state-machine event queue.
Because the architecture lacks strict priority lanes for critical control actions and fails to properly rate-limit incoming messages from the remote peer, an attacker can exploit this design. During an active call, the malicious peer can flood the event queue with a barrage of junk data. When the victim taps the hang-up button, their local termination event lands behind the massive backlog of attacker-generated noise. Consequently, the application processes the junk events first, meaning the hang-up sequence is indefinitely delayed while audio and possibly video tracks continue to flow to the remote party without the victim’s knowledge.
Broad Platform Impact and Scope
The vulnerability affects any client application embedding older RingRTC builds prior to version 2.72.0. This spans multiple operating system environments where Signal operates, including Android, iOS, and desktop deployments.
While the exploit requires an active call initiated by a malicious participant who actively floods the state machine, it fundamentally undermines user trust in interface feedback. A user seeing the call UI close or pressing the disconnect button assumes hardware peripherals like microphones and cameras are instantly disengaged. This gap between interface state and underlying hardware execution creates a high-risk scenario for individuals operating in sensitive environments where conversation privacy is paramount.
Software Patching and Mitigation Strategies
Addressing the flaw requires updating the underlying communication stack. Developers and platform maintainers have rolled out RingRTC version 2.72.0, which fundamentally restructures how event queues process critical commands.
The patched implementation introduces a priority lane for vital control signals. Specifically, hang-up events now jump to the front of the queue rather than waiting behind unverified inputs, and peer-originated traffic is subjected to strict rate-limiting to prevent saturation attacks. End users are strongly encouraged to update their Signal applications immediately through their respective app stores to ensure they are running client versions incorporating RingRTC 2.72.0 or later. Furthermore, security advisories recommend verifying that active call indicators completely disappear before discussing sensitive matters.
Analysis: The Architecture of Trust in Real-Time Communications
This vulnerability exposes a fundamental architectural lesson in real-time communication software: the control plane must never share an unweighted event queue with untrusted network inputs. In distributed systems like VoIP and secure messaging clients, developers frequently rely on finite-state machines to manage complex asynchronous events such as connection drops, media stream adjustments, and user interactions. However, when security boundaries depend on the order of operations within these queues, failing to isolate administrative control signals from peer data introduces catastrophic failure modes.
For applications marketed around privacy and zero-knowledge guarantees, the stakes are exceptionally high. Users choose these platforms precisely because they trust the software interface to accurately reflect hardware states. When an attacker can subvert that trust merely by flooding a network queue, it demonstrates that UI feedback and physical reality can diverge significantly. Moving forward, software engineers working on communication protocols must adopt defensive design patterns that guarantee immediate execution for hardware-release commands, bypassing any queues exposed to external peers. This incident serves as a stark reminder that robust encryption in transit means little if the local endpoint's hardware termination logic remains vulnerable to denial-of-service manipulation.
Editorial graphic and headline text by Signal Titans.
Source: Signal bug could keep your mic – and camera – on after hangup · Notes/docs/CVEs/CVE-2026-113380 at main · Imahian/Notes · GitHub
SIGNAL TITANS
Leave a Reply