CVE-2018-4121

HIGH

Safari < 11.1 - Remote Code Execution via WebKit Memory Corruption

Title source: llm
STIX 2.1

Exploitation Summary

EIP tracks 5 public exploits for CVE-2018-4121. PoCs published by Google Security Research, FSecureLABS, jezzus.

AI-analyzed exploit summary The exploit leverages a WebAssembly parsing vulnerability in Safari where custom sections bypass ordering checks, leading to potential overflows and type confusion. The provided PoC includes a crafted HTML and WASM file that triggers a crash in Safari.

Description

An issue was discovered in certain Apple products. iOS before 11.3 is affected. Safari before 11.1 is affected. iCloud before 7.4 on Windows is affected. iTunes before 12.7.4 on Windows is affected. tvOS before 11.3 is affected. watchOS before 4.3 is affected. The issue involves the "WebKit" component. It allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption and application crash) via a crafted web site.

Exploits (5)

exploitdb WORKING POC VERIFIED
by Google Security Research · textdosmultiple
https://www.exploit-db.com/exploits/44427

The exploit leverages a WebAssembly parsing vulnerability in Safari where custom sections bypass ordering checks, leading to potential overflows and type confusion. The provided PoC includes a crafted HTML and WASM file that triggers a crash in Safari.

Classification
Working Poc 90%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: Safari (WebKit) with WebAssembly support
No auth needed
Prerequisites: Victim must open the crafted HTML file in Safari
devstral-2 · analyzed Feb 16, 2026 Full analysis →
nomisec WORKING POC 119 stars
by FSecureLABS · poc
https://github.com/FSecureLABS/CVE-2018-4121

This is a proof-of-concept exploit for CVE-2018-4121, targeting a WebAssembly (Wasm) vulnerability in Safari 11.0.3 on macOS 10.13.3. The exploit leverages heap spraying and memory corruption to achieve remote code execution (RCE) by overflowing a function section in Wasm.

Classification
Working Poc 95%
Attack Type
Rce
Complexity
Complex
Reliability
Racy
Target: Safari 11.0.3 (13604.5.6) on macOS 10.13.3 (17D47)
No auth needed
Prerequisites: Target must be running Safari 11.0.3 on macOS 10.13.3 · Attacker must serve the exploit via a malicious webpage
devstral-2 · analyzed Feb 16, 2026 Full analysis →
nomisec WORKING POC
by jezzus · poc
https://github.com/jezzus/CVE-2018-4121

This is a proof-of-concept exploit for CVE-2018-4121, targeting a WebAssembly (Wasm) vulnerability in Safari 11.0.3 on macOS 10.13.3. The exploit leverages heap spraying and memory corruption to achieve remote code execution (RCE) by overflowing a function section in Wasm.

Classification
Working Poc 95%
Attack Type
Rce
Complexity
Complex
Reliability
Racy
Target: Safari 11.0.3 (13604.5.6) on macOS 10.13.3 (17D47)
No auth needed
Prerequisites: Compiled payload as a dylib with a constructor · Python script to convert payload to JS array · Web server to host exploit files
devstral-2 · analyzed Feb 16, 2026 Full analysis →
nomisec WORKING POC
by likekabin · poc
https://github.com/likekabin/CVE-2018-4121

This is a proof-of-concept exploit for CVE-2018-4121, targeting a WebAssembly (Wasm) vulnerability in Safari 11.0.3 on macOS 10.13.3. The exploit leverages heap spraying and memory corruption to achieve remote code execution (RCE).

Classification
Working Poc 95%
Attack Type
Rce
Complexity
Complex
Reliability
Racy
Target: Safari 11.0.3 (13604.5.6) on macOS 10.13.3 (17D47)
No auth needed
Prerequisites: Victim must visit a malicious webpage · Specific versions of Safari and macOS
devstral-2 · analyzed Feb 16, 2026 Full analysis →
inthewild WORKING POC
poc
https://github.com/mwrlabs/cve-2018-4121

This repository contains a functional proof-of-concept exploit for CVE-2018-4121, targeting Safari 11.0.3 on macOS 10.13.3. The exploit leverages a WebAssembly (Wasm) section vulnerability to achieve remote code execution (RCE) via heap manipulation and vtable corruption.

Classification
Working Poc 95%
Attack Type
Rce
Complexity
Complex
Reliability
Racy
Target: Safari 11.0.3 (13604.5.6) on macOS 10.13.3 (17D47)
No auth needed
Prerequisites: Compiled payload as a dylib with a constructor · Python script to convert payload to JS array · Web server to host exploit files
devstral-2 · analyzed Feb 23, 2026 Full analysis →

References (10)

Core 10
Core References
Third Party Advisory, VDB Entry vdb-entry x_refsource_sectrack
http://www.securitytracker.com/id/1040604
Vendor Advisory x_refsource_confirm
https://support.apple.com/HT208698
Third Party Advisory vendor-advisory x_refsource_gentoo
https://security.gentoo.org/glsa/201808-04
Vendor Advisory x_refsource_confirm
https://support.apple.com/HT208696
Vendor Advisory x_refsource_confirm
https://support.apple.com/HT208693
Vendor Advisory x_refsource_confirm
https://support.apple.com/HT208694
Exploit, Third Party Advisory x_refsource_misc
https://github.com/mwrlabs/CVE-2018-4121
Vendor Advisory x_refsource_confirm
https://support.apple.com/HT208697
Exploit, Third Party Advisory, VDB Entry exploit x_refsource_exploit-db
https://www.exploit-db.com/exploits/44427/
Vendor Advisory x_refsource_confirm
https://support.apple.com/HT208695

Scores

CVSS v3 8.8
EPSS 0.3861
EPSS Percentile 97.4%
Attack Vector NETWORK
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Details

CWE
CWE-119
Status published
Products (6)
apple/icloud < 7.4
apple/iphone_os < 11.3
apple/itunes < 12.7.4
apple/safari < 11.1
apple/tvos < 11.3
apple/watchos < 4.3
Published Apr 03, 2018
Tracked Since Feb 18, 2026