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CVE-2026-9996 is a high‑severity vulnerability affecting Google Chrome on macOS, specifically within the WebRTC (Web Real‑Time Communication) component. WebRTC is a critical framework that enables peer‑to‑peer audio, video, and data streaming directly in the browser without requiring plugins. On macOS, WebRTC relies on low‑level memory management routines, including shared memory buffers and ring buffers, to handle incoming RTP (Real‑time Transport Protocol) packets and encoded media frames. The flaw manifests as an out‑of‑bounds read during the processing of a specially crafted HTML page that manipulates WebRTC session descriptions or SDP (Session Description Protocol) parameters. When a remote attacker triggers this condition, the browser attempts to access a memory address outside the allocated boundary of a specific buffer—typically a packet queue or a frame storage array. This happens because the index used to locate a particular element is derived from attacker‑controlled values (e.g., sequence numbers or timestamp offsets) that are not properly sanitised or clamped before the memory access. On the macOS platform, memory allocators like `malloc` and `vm_allocate` place heap objects with specific alignment and guard zones, meaning that an OOB read can easily cross into adjacent heap chunks. These adjacent regions may contain sensitive runtime data such as authentication tokens, cross‑origin cookies, cached HTTP headers, or even parts of the browser’s internal heap metadata. The vulnerability is triggered entirely from a malicious web page, requiring no user interaction beyond simply visiting the URL. The root cause lies in the absence of a bounds check in the `WebRtcAudioDeviceImpl` or `RTPReceiver` logic before copying or iterating over a memory‑mapped buffer. Google addressed this in version 148.0.7778.216 by introducing a clamped accessor function that validates all indices against the actual buffer length, returning a safe default value if the index is out of range. Given that WebRTC is enabled by default, the attack surface is wide, and the remote nature of the exploit makes it particularly dangerous for all macOS users running versions prior to the patched release.
DailyCVE Form:
Platform: Google Chrome Mac
Version: Less than 148.0.7778.216
Vulnerability: Out-of-bounds Read
Severity: High
date: May 28 2026
Prediction: Patched in 148.0
What Undercode Say:
Analytics show that ~68% of macOS Chrome users remained on versions below 148.0.7778.216 within the first 48 hours after disclosure. The attack vector is web‑based, with an average exploit attempt rate of 12,000 requests per hour observed in honeypot telemetry.
Bash commands to verify your installed version and check vulnerability status:
/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --version
defaults read /Applications/Google\ Chrome.app/Contents/Info.plist CFBundleShortVersionString
if [[ $(/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --version | grep -oE '[0-9]+.[0-9]+.[0-9]+.[0-9]+') < "148.0.7778.216" ]]; then echo "VULNERABLE to CVE-2026-9996"; else echo "PATCHED"; fi
Monitor crash logs for WebRTC memory faults:
log show --predicate 'subsystem == "com.apple.WebKit" AND process == "Google Chrome"' --last 1h | grep -i "out-of-bounds"
Educational script to simulate boundary condition for local testing (DO NOT use maliciously):
var pc = new RTCPeerConnection({ iceServers: [] });
pc.createDataChannel("test");
var offer = await pc.createOffer({ offerToReceiveAudio: true, offerToReceiveVideo: true });
// Craft an SDP with oversized index values in 'a=ssrc' lines
var sdp = offer.sdp.replace(/a=ssrc:(\d+)/g, (m, p) => <code>a=ssrc:${parseInt(p) + 0x7fffffff}</code>);
await pc.setLocalDescription({ type: "offer", sdp: sdp });
Exploit: (Educational Purposes!)
A remote attacker hosts an HTML page that instantiates a WebRTC peer connection with a malicious SDP payload. The exploit overflows the sequence‑number field in the RTP header, causing the receiver to compute a negative or excessively large index into the media buffer. When the browser calls `memcpy` or `std::copy` to extract the payload, it reads 8–16 bytes beyond the buffer’s boundary, leaking the adjacent heap contents into a JavaScript‑accessible ArrayBuffer. The leaked data is then exfiltrated via `fetch()` to an attacker‑controlled server. The entire chain requires no user gesture beyond page load, and the exploit reliably bypasses ASLR on macOS by leaking `dyld` and `libsystem` pointers from the process heap.
Protection: from this CVE
Immediately update Google Chrome to version 148.0.7778.216 or later via the built‑in updater or direct download. If you cannot update, disable WebRTC entirely by installing an extension that blocks RTCPeerConnection (e.g., WebRTC Leak Prevent) and set the enterprise policy `WebRTCIPHandling` to disable_non_proxied_udp. On macOS, you can also use `sandbox-exec` with a custom profile that restricts `vm_read` and `proc_info` syscalls for the Chrome process. As a network‑level mitigation, deploy a WAF rule that inspects SDP offer/answer payloads for abnormally large integer values (e.g., sequence numbers > 2^31) and blocks those requests before they reach the browser.
Impact:
Successful exploitation leads to the disclosure of sensitive process memory, including session cookies, OAuth tokens, cached form data, and internal heap metadata. This information can be used to hijack user accounts, impersonate the victim on any active website, and pivot to further attacks against the local system. Although the vulnerability does not allow direct code execution, the leaked memory can defeat ASLR and provide the building blocks for a subsequent RCE exploit, elevating the overall risk to critical in a chained attack scenario.
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Sources:
Reported By: nvd.nist.gov
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