VulnerabilityPublished 27 Oct 2026

CVE-2026-118021: Sandbox Escape Due to Use-after-free

Source GCVE Database

Authoritative record:CVE-2026-118021· High

Not known to be exploited.

Data as of 27 Oct 2026, 16:43 UTC

Severity

High

Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD

Exploitation evidence

Disclosed: evidence found.
CVE published 27 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-3hc8-89qm-6758

What to do

AI-suggested

Users and administrators should update Firefox to version 159 or later, where this vulnerability has been fixed. Applying this official fix fully mitigates the risk associated with this issue.

Description

CVE-2026-118021 is a use-after-free vulnerability in the XPCOM component of Firefox that allows sandbox escape. This security flaw was addressed and fixed in Firefox version 159. The vulnerability is classified as high impact due to its potential to break sandbox protections.

Impact

Successful exploitation of this use-after-free vulnerability could allow an attacker to escape the sandbox, potentially leading to execution of arbitrary code with elevated privileges outside the browser's restricted environment. This poses a significant security risk as it undermines the browser's defense-in-depth model.

Summary

This vulnerability involves a use-after-free condition in the XPCOM component of Firefox, which can be exploited to escape the browser's sandbox environment. The sandbox is a critical security mechanism designed to isolate browser processes and limit the impact of exploits. The flaw was identified and resolved by Mozilla in Firefox 159, mitigating the risk of sandbox escape through this vector.

References

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