How severe is CVE-2018-5163?

CVE-2018-5163 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2018-5163 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (80th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-5163?

CVE-2018-5163 primarily affects Mozilla Firefox. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2018-5163?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2018-5163 published?

CVE-2018-5163 was published on 2018-06-11 and last updated on 2026-06-17.

CVE-2018-5163

CVE-2018-5163 is a high-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 8.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-281.

Key facts

Severity: High (CVSS 3.x base score 8.1)
CVSS v2: 5.1
EPSS exploit prediction: 2% (80th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-281
Affected product: Mozilla Firefox
Published: 2018-06-11
Last modified: 2026-06-17

Description

If a malicious attacker has used another vulnerability to gain full control over a content process, they may be able to replace the alternate data resources stored in the JavaScript Start-up Bytecode Cache (JSBC) for other JavaScript code. If the parent process then runs this replaced code, the executed script would be run with the parent process' privileges, escaping the sandbox on content processes. This vulnerability affects Firefox < 60.

Frequently asked questions

What is CVE-2018-5163?: If a malicious attacker has used another vulnerability to gain full control over a content process, they may be able to replace the alternate data resources stored in the JavaScript Start-up Bytecode Cache (JSBC) for other JavaScript code. If the parent process then runs this replaced code, the executed script would be run with the parent process' privileges, escaping the sandbox on content processes. This vulnerability affects Firefox < 60.
How severe is CVE-2018-5163?: CVE-2018-5163 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2018-5163 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (80th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-5163?: CVE-2018-5163 primarily affects Mozilla Firefox. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2018-5163?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2018-5163 published?: CVE-2018-5163 was published on 2018-06-11 and last updated on 2026-06-17.

References

Affected products (5)

cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:17.10:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*

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