Description

Denial-of-service in the Networking component. This vulnerability was fixed in Firefox 157.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "6.5",
  "pubDate": "2026-09-29T13:17:44.550Z",
  "pubdate": "2026-09-29T13:17:44.550Z",
  "executiveSummary": "A denial-of-service (DoS) vulnerability has been identified within the Networking component of the Firefox web browser. This flaw allows a remote, unauthenticated attacker to disrupt browser availability, leading to application instability or unexpected termination.\nThe vulnerability resides in the core networking stack, which handles protocol communication and resource management. By sending specifically crafted network traffic or triggering complex networking states, an attacker can induce a state of resource exhaustion or a logic error that crashes the browser process.\nThe risk implication is significant as it directly impacts user accessibility and browser stability. Exploitation does not require prior authentication or elevated privileges, making it accessible to remote actors. The primary impact is the complete loss of browser functionality until the application is restarted. This issue was officially addressed and mitigated in Firefox 157, necessitating an update for all affected users to ensure service continuity and security.",
  "technicalDetails": "The vulnerability originates within the Networking component of Firefox, which is responsible for managing low-level socket connections, protocol parsing, and data streaming. The root cause pertains to an improper handling of network state transitions or malformed data packets that trigger an unhandled exception or an assertion failure during the packet processing pipeline.\nAt a granular level, the networking stack likely encounters a condition where the state machine managing active connections or data buffers enters an inconsistent or undefined state. When the browser attempts to process these malformed packets or unexpected state transitions, it triggers a crash—potentially due to a null pointer dereference, an out-of-bounds memory access, or an infinite loop that effectively starves the main thread of CPU cycles.\nThe attack flow initiates when a malicious entity directs specifically formatted network traffic toward a target instance of Firefox. Since the vulnerability resides within the networking stack, the attack can be delivered via HTTP/HTTPS responses, WebSockets, or other protocols handled by the browser's networking library. Upon receipt of the malicious payload, the networking component fails to perform adequate input validation or bounds checking. As the component attempts to parse or route the data, the underlying logic error is triggered.\nExploitation does not necessitate authentication or specific user privileges. The attack is network-exposed, meaning any scenario where the browser interacts with an untrusted or compromised server can facilitate the exploitation of this flaw. Because the networking process runs with sufficient privileges to manage network hardware and system-level socket calls, the failure in this component is critical.\nThe post-exploitation impact is limited to a denial-of-service, manifesting as the sudden closure or hanging of the Firefox browser. While the vulnerability results in process termination, it does not explicitly imply a remote code execution (RCE) vector based on current information. However, the unexpected termination of the browser process interrupts ongoing sessions and potentially forces the user to re-authenticate with web services, impacting the overall security posture and user experience. Firefox 157 introduced necessary patches to sanitize input handling and refine the networking state machine logic to prevent these error conditions."
}