Medium

WebKit use-after-free leading to process crash

IdentifiersCVE-2026-20664CWE-416

CVE-2026-20664 is a WebKit memory-handling vulnerability affecting Safari, WebKitGTK, and WPE WebKit. Apple and WebKitGTK describe the issue as occurring when processing maliciously crafted web content, which may lead to an unexpected process crash, and state that it was fixed through improved memory handling. Supporting technical context indicates the underlying flaw involved stale pointer handling after growth of non-shared resizable WebAssembly memory in JavaScriptCore: after memory.grow(), buffer metadata could be updated while m_data still referenced the old freed allocation, leaving a stale typed-array view over freed Primitive Gigacage memory. Public research further describes this memory corruption primitive as part of a broader Safari exploit chain, but the vendor advisory for CVE-2026-20664 itself characterizes the impact as a crash rather than code execution.

For your environment

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can cause the targeted WebKit/Safari renderer process to crash while handling attacker-controlled web content, resulting in denial of service for the affected browsing context. Although external research describes use of the underlying memory flaw in a broader exploit chain to expose cross-origin data, the vendor-published impact for CVE-2026-20664 is limited to unexpected process crash.

Mitigation

If you can’t patch tonight, do this now.

Until patches are deployed, reduce exposure by limiting use of untrusted web content in affected WebKit-based browsers and embedded WebKit consumers, and prioritize updates for internet-exposed client systems. For Linux environments using WebKitGTK or WPE WebKit, upgrade affected packages to 2.52.1 or later from the distribution/vendor. No specific configuration-based workaround is provided in the supplied content.

Remediation

Patch, then assume compromise.

Apply the vendor fixes: Safari 26.4; iOS 26.4 and iPadOS 26.4; macOS Tahoe 26.4; visionOS 26.4; and WebKitGTK/WPE WebKit 2.52.1 or later. Apple states the issue was addressed with improved memory handling.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

AppleIpadosoperating_system

AppleIphone Osoperating_system

AppleMacosoperating_system

AppleSafariapplication

AppleVisionosoperating_system

Rocky LinuxRocky Linuxoperating_system

WebkitgtkWebkit2gtk3application

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

12 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

12 SOURCESView more in app

imperva blogNews

Apr 23, 2026

Hacking Safari with GPT 5.4 | Imperva

A Safari/WebKit vulnerability chaining a stale WebAssembly resizable buffer pointer with Fetch opaque-response cloning behavior to break the Same-Origin Policy and leak authenticated cross-origin data such as access tokens and other sensitive information.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity7