There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - When Web Render components were destructed, a race condition could have caused undefined behavior, and we
    presume that with enough effort may have been exploitable to run arbitrary code. This vulnerability
    affects Firefox < 88.0.1 and Firefox for Android < 88.1.3. (CVE-2021-29952)

The remote Ubuntu 18.04 LTS / 20.04 LTS host has packages installed that are affected by a vulnerability as referenced in the USN-4942-1 advisory.

    A race condition was discovered in Web Render Components. If a user were tricked into opening a specially     crafted website, an attacker could potentially exploit this to execute arbitrary code.

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The version of Firefox installed on the remote Windows host is prior to 88.0.1. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2021-20 advisory.

  - When Web Render components were destructed, a race condition could have caused undefined behavior, and we     presume that with enough effort may have been exploitable to run arbitrary code. (CVE-2021-29952)

  - By triggering multiple pop-up prompts containing <code>javascript:</code> URLs, a malicious webpage could     have forced a Firefox for Android user into executing attacker-controlled JavaScript in the context of     another domain, resulting in a Universal Cross-Site Scripting vulnerability. Note: This issue only     affected Firefox for Android. Other operating systems are unaffected. (CVE-2021-29953)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - When Web Render components were destructed, a race condition could have caused undefined behavior, and we     presume that with enough effort may have been exploitable to run arbitrary code. This vulnerability     affects Firefox < 88.0.1 and Firefox for Android < 88.1.3. (CVE-2021-29952)

Note that Nessus relies on the presence of the package as reported by the vendor.

The version of Firefox installed on the remote macOS or Mac OS X host is prior to 88.0.1. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2021-20 advisory.

  - When Web Render components were destructed, a race condition could have caused undefined behavior, and we     presume that with enough effort may have been exploitable to run arbitrary code. (CVE-2021-29952)

  - By triggering multiple pop-up prompts containing <code>javascript:</code> URLs, a malicious webpage could     have forced a Firefox for Android user into executing attacker-controlled JavaScript in the context of     another domain, resulting in a Universal Cross-Site Scripting vulnerability. Note: This issue only     affected Firefox for Android. Other operating systems are unaffected. (CVE-2021-29953)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Published	Updated	Severity
427335	Alpine: multiple librewolf packages: security update to 88.0.1-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	5/16/2025	7/2/2026	high
404381	Alpine: multiple firefox packages: security update to 88.0.1-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	10/31/2023	7/2/2026	high
404381	Alpine: multiple firefox packages: security update to 88.0.1-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	10/31/2023	7/2/2026	high
427335	Alpine: multiple librewolf packages: security update to 88.0.1-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	5/16/2025	7/2/2026	high
149409	Ubuntu 18.04 LTS / 20.04 LTS : Firefox vulnerability (USN-4942-1)	Nessus	Ubuntu Local Security Checks	5/12/2021	8/27/2024	high
149281	Mozilla Firefox < 88.0.1	Nessus	Windows	5/5/2021	11/18/2025	high
248515	Linux Distros Unpatched Vulnerability : CVE-2021-29952	Nessus	Misc.	8/12/2025	7/28/2026	high
149282	Mozilla Firefox < 88.0.1	Nessus	MacOS X Local Security Checks	5/5/2021	11/18/2025	high

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