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CVE Record

CVE-2026-4687: Sandbox escape due to incorrect boundary conditions in the Telemetry component

Sandbox escape due to incorrect boundary conditions in the Telemetry component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

CriticalCVSS 9.6Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

CVE-2026-4687 is a critical Mozilla sandbox escape in the Telemetry component. A user would need to interact with malicious content, but successful exploitation could break browser or mail-client isolation and threaten data confidentiality, integrity, and availability.

Executive priority

Treat this as urgent patching for browser and email fleets. There is no source-backed active exploitation claim, but the critical score and sandbox escape impact justify rapid remediation, especially on user workstations and sensitive environments.

Technical view

The issue is described as incorrect boundary conditions in Telemetry, mapped to CWE-120 and CWE-501. CVSS 9.6 indicates network attackability, low complexity, no privileges, required user interaction, changed scope, and high impact across confidentiality, integrity, and availability.

Likely exposure

Organizations using Mozilla Firefox or Thunderbird should check for installations below the fixed releases: Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9. Red Hat environments should also review relevant RHSA errata.

Exploitation context

The provided bundle does not show CISA KEV listing or cited evidence of active exploitation. The risk remains high because sandbox escape vulnerabilities can turn user interaction with malicious content into broader compromise beyond the intended application boundary.

Researcher notes

The source bundle names the component and fixed versions but does not provide exploit details or a full vulnerable-version range. Bugzilla and vendor advisories should be used for confirmation, while avoiding assumptions beyond Mozilla and Red Hat statements.

Mitigation direction

  • Update Firefox to 149, ESR 115.34, or ESR 140.9, as applicable.
  • Update Thunderbird to 149 or 140.9, as applicable.
  • Apply relevant Red Hat RHSA updates for packaged Firefox or Thunderbird.
  • Check Mozilla and distribution advisories for any product-specific guidance.
  • Prioritize managed endpoints, VDI images, and systems handling sensitive email or browsing workflows.

Validation and detection

  • Inventory Firefox and Thunderbird versions across endpoints and servers.
  • Confirm installed versions meet or exceed the fixed releases listed by Mozilla.
  • Review Red Hat package advisory status where Mozilla products come from Red Hat repositories.
  • Verify endpoint management reports successful deployment, not only update availability.
  • Check vulnerability scanner detections against Mozilla and Red Hat advisory identifiers.
Prepared
Confidence
medium
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-120: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-501: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
description · low confidence lookup

Privilege behavior lookup

The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-4687 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.6 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
35Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: total

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
9.6CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H2.86CISA-ADP
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H1.65.9redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

9.6Critical
CVSS 3.1 vector shape for CVE-2026-4687Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
redhat-SADPfirefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Telemetry component
other:Red Hat severity ratingcvssV3_1
  • 2026-03-24T13:03:48.511Z: Reported to Red Hat.
  • 2026-03-24T12:30:22.179Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox115.34, 140.9, 149Listed
MozillaThunderbird140.9, 149Listed
Weakness

CWE details

CWE-120CWE-501

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-120 · source CWE mapping

Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-501 · source CWE mapping

Trust Boundary Violation

Trust Boundary Violation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs