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/DISPATCH · 2026-08-19

Apple Safari 26.6.1 Patches 22 WebKit Vulnerabilities: CVE-2026-65346 ImageIO Integer Overflow Enables One-Click Arbitrary Code Execution

Apple released Safari 26.6.1 and macOS Tahoe 26.6.2 on 18 August. Nine of 22 WebKit CVEs were reported by OpenAI Codex Security. CVE-2026-65346 ImageIO integer overflow can trigger one-click arbitrary code execution. CVE-2026-64778 WebKit History can leak sensitive data when a victim visits a malicious site.

Apple released Safari 26.6.1 (macOS Sonoma, Sequoia), macOS Tahoe 26.6.2, iOS / iPadOS 26.6.1, and 18.7.10 security updates on 17–18 August 2026. The bulletin lists 22 WebKit-related CVEs plus multiple kernel, ImageIO, IOGPUFamily, Telephony, and Audio defects. macOS Tahoe 26.6.2 also packages several fixes previously shipped only on the beta channel, so the actual impact of the set exceeds the 22 WebKit CVEs.

Incident Overview

9to5Mac and Apple's official security notes show 9 of the 22 WebKit CVEs patched in Safari 26.6.1 were reported by OpenAI Codex Security (~41%). Remaining credits include Cisco Talos, TrendAI Zero Day Initiative, Calif.io, Braze Security Team, Out of Bounds, and Citadelo. High-impact items: CVE-2026-65346 (ImageIO integer overflow; malicious image can trigger arbitrary code execution), CVE-2026-64778 (WebKit History; visiting a malicious site can leak sensitive data), and application-data-access issues CVE-2026-28958 / CVE-2026-28996. CISA added macOS Screen Sharing authentication bypass CVE-2026-65400 to the KEV catalog and mandated federal patching by 21 August. NCSC-NL earlier confirmed CVE-2026-65400 was used to plant a Monero miner on macOS hosts with port 5900 exposed to the internet.

Technical Details

Impact Assessment

WebKit is Apple's unified browser engine across platforms and a primary entry in the browser 0-day attack chain. Boynton notes a single memory-corruption bug is not RCE, but historically WebKit memory-corruption bugs have been chained into full exploit chains for commercial spyware vendors (NSO Group Pegasus, Intellexa Predator). OpenAI Codex Security reporting 9 CVEs from a single source strongly signals an inflection in AI-assisted vuln research: traditional disclosure is monthly; GPU plus multi-agent workflows can now produce 9 independent WebKit CVEs in a short window, forcing Apple to merge fixes that would have been spread across later months. Jamf and SentinelOne note enterprises should prioritize non-WebKit components such as ImageIO and Telephony: those surfaces are often ignored by standing MDM yet are the easiest to reach on executive devices via SMS, email attachments, or malicious ad slots.

Remediation

References