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Fencer Vulns
high 8.1

CVE-2018-5163 json

If a malicious attacker has used another vulnerability to gain full control over a content process, they may be able to replace the alterna…

published 2018-06-11 8 y ago modified 2026-06-17 4 mo ago also EUVD-2018-16948

cvss
8.1
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.0%
EPSS 2.0% chance of exploitation in 30 days, percentile 81%
public exploits
0
none known

Summary

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.

Patch / fix

  • Mozilla Firefox 60
  • firefox Ubuntu 14.04 LTS 60.0+build2-0ubuntu0.14.04.1
  • firefox Ubuntu 16.04 LTS 60.0+build2-0ubuntu0.16.04.1
  • firefox Ubuntu 18.04 LTS 60.0+build2-0ubuntu1

ubuntu advisories UBUNTU-CVE-2018-5163

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • MozillaFirefox SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +17 more 68.2.0-109.95.2

suse advisories SUSE-SU-2019:2872-1

  • firefox-esr openSUSE Tumbleweed 128.5.1-1.1
  • MozillaFirefox openSUSE Tumbleweed 92.0-1.2

opensuse advisories openSUSE-SU-2024:14572-1openSUSE-SU-2024:10600-1

  • firefox Arch Linux 60.0-1

arch linux advisories AVG-693

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2018-5163 updated cvss 8.1

Mozilla: Replacing cached data in JavaScript Start-up Bytecode Cache

  • Red Hat Enterprise Linux 6 firefox, thunderbird Red Hat Enterprise Linux 7 firefox, thunderbird
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.04% chance of exploitation in the next 30 days, higher than 81% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.0 8.1 CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 5.1 AV:N/AC:H/Au:N/C:P/I:P/A:P

Affected products

  • Mozilla Firefox

Classification

Weakness
  • CWE-281 Improper Preservation of Permissions

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.