Not ratedCVE-2026-117864

    Sandbox escape in the Form Manager component (CVE-2026-117864)

    Published Last modified Sources: HKCERT, Debian, Mozilla Mfsa, CVE.org, pwn.watch

    What is affected, what to do

    Sandbox escape in the Form Manager component. This vulnerability was fixed in Firefox 159, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

    The available sources name no fixed version. Check the vendor guidance in the references below.

    Affected
    • Debian Firefox-esr 153.6.0esr-1~deb13u1..*

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

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    Priority

    No value is available for this vulnerability.

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    CVSS v3

    No value is available for this vulnerability.

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    EPSS score

    No value is available for this vulnerability.

    Show all metrics
    Severity
    Not rated
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    30.00 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
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    Published

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    Sandbox escape in the Form Manager component. This vulnerability was fixed in Firefox 159, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

    Source: HKCERT (CC BY 3.0 HK) · HKCERT rating: medium, Debian Security Advisories, mozilla_mfsa, cvelistv5, NVD (NIST), pwn.watch

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianfirefox-esrtrixie

    References & sources

    • bugzilla.mozilla.orgshow_bug.cgi?id=2058614
    • mozilla.orgsecurity/advisories/mfsa2026-118
    • mozilla.orgsecurity/advisories/mfsa2026-120
    • pwn.watchpwn.watch: Firefox 159 and Firefox ESR 153.6 and 115.44 fix 167 bugs, including 13 sandbox escapespwn-watch
    • mozilla.orgMFSA 2026-118: Security Vulnerabilities fixed in Firefox 159pwn-watch
    • mozilla.orgMFSA 2026-120: Security Vulnerabilities fixed in Firefox ESR 153.6pwn-watch
    • mozilla.orgMFSA 2026-119: Security Vulnerabilities fixed in Firefox ESR 115.44pwn-watch
    • NVD (NIST)NVD: CVE-2026-117861pwn-watch
    • mozilla.orgMFSA 2026-121: Security Vulnerabilities fixed in Thunderbird 159pwn-watch
    • mozilla.orgsecurity/advisories/mfsa2026-121
    • mozilla.orgsecurity/advisories/mfsa2026-122

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedMozilla

      Description added or changed

      Show 4 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionchanged
      Sandbox escape in the Form Manager component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.
      Sandbox escape in the Form Manager component. This vulnerability was fixed in Firefox 159, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.
      Affected versions (publisher)added
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      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/117xxx/CVE-2026-117864.json">CVE-2026-117864</a>
      Referenceadded
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      https://www.mozilla.org/security/advisories/mfsa2026-121/
      Referenceadded
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      https://www.mozilla.org/security/advisories/mfsa2026-122/

      Source identifier: security@mozilla.org

    2. ReceivedMozilla

      Description added or changed

      Show 5 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      Sandbox escape in the Form Manager component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/117xxx/CVE-2026-117864.json">CVE-2026-117864</a>
      Referenceadded
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      https://bugzilla.mozilla.org/show_bug.cgi?id=2058614
      Referenceadded
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      https://www.mozilla.org/security/advisories/mfsa2026-118/
      Referenceadded
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      https://www.mozilla.org/security/advisories/mfsa2026-120/

      Source identifier: security@mozilla.org

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