CriticalCVE-2026-12297

    Sandbox escape due to incorrect boundary conditions in the Networking component (CVE-2026-12297)

    Published Last modified Sources: SUSE, CVE.org, Debian LTS, Mozilla Mfsa, Debian, BSI

    What is affected, what to do

    Sandbox escape due to incorrect boundary conditions in the Networking component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.

    Update Mozilla Firefox to version 115.37.0, Mozilla Firefox to version 152.0.0, Mozilla Firefox to version 140.12.0.

    Affected
    • Mozilla Firefox lt *..115.37.0
    • Mozilla Firefox lt *..152.0.0
    • Mozilla Firefox lt 128.0..140.12.0
    • Mozilla Thunderbird lt *..140.12.0
    • Mozilla Thunderbird lt *..152.0.0
    Fixed in
    • Mozilla Firefox 115.37.0
    • Mozilla Firefox 152.0.0
    • Mozilla Firefox 140.12.0
    • Mozilla Thunderbird 140.12.0
    • Mozilla Thunderbird 152.0.0

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

    Metrics

    9.6

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    9.6

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: SUSE, CVE.org, Debian LTS, Mozilla Mfsa, Debian, BSI

    0.4 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 33.3

    Show all metrics
    Severity
    Critical
    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
    75.96 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
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    9.6 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.6
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    0.4 %
    Low — model estimates < 1% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    33.3
    Elevated — this CVE ranks above at least 10% of all CVEs scored today.
    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
    —
    Published
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-119, CWE-653

    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
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    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 due to incorrect boundary conditions in the Networking component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.

    Source: suse_csaf, cvelistv5, NVD (NIST), CVE.org (MITRE), Debian LTS Advisories, mozilla_mfsa, Debian Security Advisories, BSI WID Portal, BSI CSAF

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    mozillafirefox
    • < 115.37.0
    • 128.0 – < 140.12.0
    • < 152.0.0
    • 115.37.0
    • 140.12.0
    • 152.0.0
    mozillathunderbird
    • < 152.0.0
    • < 140.12.0
    • 152.0.0
    • 140.12.0

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianfirefox-esrbookworm
    Linuxdebianfirefox-esrbullseye
    Linuxdebianfirefox-esrtrixie
    Linuxdebianthunderbirdbookworm
    Linuxdebianthunderbirdbullseye
    Linuxdebianthunderbirdtrixie

    Weakness classes (CWE)

    • CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer

      Class

      The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

      Entry at MITRE CWE-119

    • CWE-653Improper Isolation or Compartmentalization

      Class

      The product does not properly compartmentalize or isolate functionality, processes, or resources that require different privilege levels, rights, or permissions.

      Entry at MITRE CWE-653

    References & sources

    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 modifiedRed Hat ADP

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:37210
      Affected versions (publisher)changed
      Red Hat Enterprise Linux AppStream EUS (v. 10.0), Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux AppStream (v. 8) (+9)
      Red Hat Enterprise Linux AppStream EUS (v. 10.0), Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux AppStream (v. 8) (+11)

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    2. Initial analysis by NVDNVD

      Newly listed as affected:
      Show 7 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationadded
      —
      OR *cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:* versions up to (excluding) 152.0.0 *cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:* versions up to (excluding) 115.37.0 *cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:* versions up to (excluding) 152.0.0 *cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:* versions up to (excluding) 140.12.0 *cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:* versions from (including) 128.0 up to (excluding) 140.12.0
      Reference typeadded
      —
      Mozilla Corporation: https://bugzilla.mozilla.org/show_bug.cgi?id=2041610 Types: Permissions Required
      Reference typeadded
      —
      Mozilla Corporation: https://www.mozilla.org/security/advisories/mfsa2026-57/ Types: Vendor Advisory
      Reference typeadded
      —
      Mozilla Corporation: https://www.mozilla.org/security/advisories/mfsa2026-58/ Types: Vendor Advisory
      Reference typeadded
      —
      Mozilla Corporation: https://www.mozilla.org/security/advisories/mfsa2026-59/ Types: Vendor Advisory
      Reference typeadded
      —
      Mozilla Corporation: https://www.mozilla.org/security/advisories/mfsa2026-60/ Types: Vendor Advisory
      Reference typeadded
      —
      Mozilla Corporation: https://www.mozilla.org/security/advisories/mfsa2026-61/ Types: Vendor Advisory

      Source identifier: nvd@nist.gov

    3. Record modifiedCISA ADP

      CVSS V3.1: AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Weakness type: CWE-119

      Show 3 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      CVSSadded
      —
      AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
      Weakness type (CWE)added
      —
      CWE-119
      SSVC assessmentadded
      —
      {"id":"CVE-2026-12297","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-06-18T14:05:00.908905Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    4. Record modifiedMozilla

      Description added or changed

      Show 3 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionchanged
      Sandbox escape due to incorrect boundary conditions in the Networking component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, and Firefox ESR 115.37.
      Sandbox escape due to incorrect boundary conditions in the Networking component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.
      Referenceadded
      —
      https://www.mozilla.org/security/advisories/mfsa2026-60/
      Referenceadded
      —
      https://www.mozilla.org/security/advisories/mfsa2026-61/

      Source identifier: security@mozilla.org

    One NVD translation into another language is hidden.

    Linked advisories

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