CVE-2024-7652 Overview
CVE-2024-7652 is a type confusion vulnerability rooted in the ECMA-262 JavaScript specification's handling of Async Generators. The flaw affects Mozilla Firefox, Firefox ESR, and Thunderbird, where incorrect specification logic could trigger memory corruption inside the SpiderMonkey JavaScript engine. Attackers can leverage the condition to produce an exploitable crash through crafted web content. The issue is tracked under [CWE-476] (NULL Pointer Dereference) and carries network-based exploitability without authentication or user interaction.
Critical Impact
A remote attacker can deliver malicious JavaScript that triggers type confusion in Async Generator handling, leading to memory corruption and process crash in affected Mozilla products.
Affected Products
- Mozilla Firefox versions prior to 128
- Mozilla Firefox ESR versions prior to 115.13
- Mozilla Thunderbird versions prior to 115.13 and prior to 128
Discovery Timeline
- 2024-09-06 - CVE-2024-7652 published to NVD
- 2025-04-04 - Last updated in NVD database
Technical Details for CVE-2024-7652
Vulnerability Analysis
The vulnerability originates in the ECMA-262 specification itself, specifically the algorithm describing how Async Generator objects manage their internal state and queued requests. Mozilla's SpiderMonkey engine implemented the specification as written, inheriting the flawed behavior. When the engine processes certain sequences of async generator operations, it treats an object as a type that it is not, producing a type confusion condition. This confusion translates into memory corruption inside the JavaScript runtime, which can produce an exploitable crash.
The coordinated disclosure spans the TC39 ECMA-262 specification and Mozilla's downstream implementation reported in Mozilla Bug 1901411. Because the bug is a language-level defect, multiple JavaScript engines required coordinated remediation.
Root Cause
The root cause is incorrect handling in the Async Generator state machine defined by ECMA-262. The specification permitted a sequence of operations that allowed an internal value to be interpreted with the wrong type tag. SpiderMonkey's adherence to that specification surfaced the defect at runtime, where a corrupted pointer or object header could be dereferenced.
Attack Vector
Exploitation requires an attacker to deliver crafted JavaScript to a victim. In Firefox, this is achieved by loading a malicious or compromised web page. In Thunderbird, scripted content rendered through HTML email or remote content can trigger the same code paths. No authentication or user interaction beyond visiting attacker-controlled content is required.
The vulnerability primarily produces an availability impact through process crashes, though Mozilla notes the crash is potentially exploitable for further compromise. No verified public exploit code is available for this CVE.
Detection Methods for CVE-2024-7652
Indicators of Compromise
- Repeated, unexpected crashes of firefox.exe, firefox-bin, or thunderbird processes correlating with specific browsing sessions or message previews
- Crash telemetry referencing SpiderMonkey async generator stack frames such as AsyncGeneratorResume or AsyncGeneratorYield
- Outbound requests from browser hosts to recently registered domains followed by abnormal process termination
Detection Strategies
- Inventory installed Firefox, Firefox ESR, and Thunderbird builds and flag any version below the patched releases (Firefox 128, Firefox ESR 115.13, Thunderbird 115.13/128)
- Monitor endpoint crash logs and Windows Error Reporting (WER) data for clusters of Mozilla product crashes on the same URL or message
- Correlate web proxy logs with crash events to identify pages that consistently trigger renderer faults
Monitoring Recommendations
- Forward browser crash telemetry into a centralized analytics platform for trend analysis across the fleet
- Alert on Mozilla product versions detected in software inventory that predate the fixed builds
- Track DNS and HTTP telemetry for sessions immediately preceding browser process termination to surface drive-by content
How to Mitigate CVE-2024-7652
Immediate Actions Required
- Upgrade Firefox to version 128 or later, Firefox ESR to 115.13 or later, and Thunderbird to 115.13 or 128 or later
- Validate that managed enterprise update channels are enabled and not pinned to vulnerable builds
- Disable JavaScript execution in Thunderbird message rendering where business needs allow
Patch Information
Mozilla addressed the issue in the following advisories: MFSA-2024-29, MFSA-2024-30, MFSA-2024-31, and MFSA-2024-32. The corresponding TC39 specification change is documented in GHSA-g38c-wh3c-5h9r.
Workarounds
- Restrict execution of untrusted JavaScript using enterprise policy controls or extensions such as content blockers
- Configure Thunderbird to block remote content and disable JavaScript in message display where feasible
- Apply network egress filtering and DNS reputation services to reduce exposure to malicious sites until patches are deployed
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
