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CVE Record

CVE-2026-8401: Sandbox escape in the Profile Backup component

Sandbox escape in the Profile Backup component. This vulnerability was fixed in Firefox 150.0.3, Firefox ESR 115.36, Firefox ESR 140.11, and Thunderbird 140.11.

CriticalCVSS 9.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

CVE-2026-8401 is a critical Mozilla sandbox escape in the Profile Backup component. A sandbox escape can let malicious content break out of browser containment and reach broader system resources. Mozilla states the issue was fixed in Firefox 150.0.3, Firefox ESR 115.36/140.11, and Thunderbird 140.11.

Executive priority

Treat as urgent endpoint patching. The issue is critical, affects common browser and mail software, and breaks sandbox isolation. No active exploitation is evidenced in the provided sources, but delay increases exposure if exploit details emerge.

Technical view

The CVE describes a sandbox escape in Mozilla's Profile Backup component, mapped to CWE-653 and CWE-693. The CVSS 3.1 score is 9.8 with network attack vector, low complexity, no privileges, no user interaction, and high confidentiality, integrity, and availability impact.

Likely exposure

Exposure centers on systems running Mozilla Firefox, Firefox ESR, or Thunderbird that have not received the fixed releases named by Mozilla. Red Hat references show downstream Linux packages also required security handling. Browser and mail-client inventories, especially ESR deployments, should be checked first.

Exploitation context

The provided bundle does not show CISA KEV listing or cite active exploitation. Treat this as high urgency because sandbox escapes in widely deployed browsers can become valuable quickly, but do not claim exploitation without vendor or KEV confirmation.

Researcher notes

Sources identify the component and fixed versions but do not provide public technical root-cause detail in this bundle. Avoid assuming a specific trigger path. Validation should focus on product/channel version mapping, vendor advisory correlation, and downstream package status.

Mitigation direction

  • Update Firefox to 150.0.3, or ESR 115.36/140.11 where applicable.
  • Update Thunderbird to 140.11 where Thunderbird is deployed.
  • Apply applicable Red Hat security advisories for managed Linux fleets.
  • Check Mozilla and OS vendor guidance for any superseding fixed builds.
  • Prioritize unmanaged endpoints and long-lived ESR installations.

Validation and detection

  • Inventory Firefox, Firefox ESR, and Thunderbird versions across endpoints.
  • Confirm installed versions match Mozilla's fixed releases for each channel.
  • Review Red Hat advisory applicability for affected Linux packages.
  • Check vulnerability scanners for CVE-2026-8401 coverage and false negatives.
  • Verify patch deployment through endpoint management or package-manager records.
Prepared
Confidence
high
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-653: 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-693: 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-2026-8401 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
9.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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
30Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical 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
9.8CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9CISA-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

9.8Critical
CVSS 3.1 vector shape for CVE-2026-8401Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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 in the Profile Backup component
other:Red Hat severity ratingcvssV3_1
  • 2026-05-12T15:01:19.809Z: Reported to Red Hat.
  • 2026-05-12T14:24:33.320Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox115.36, 140.11, 150.0.3Listed
MozillaThunderbird140.11Listed
Weakness

CWE details

CWE-653CWE-693

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

CWE-653 · source CWE mapping

Improper Isolation or Compartmentalization

Improper Isolation or Compartmentalization represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-693 · source CWE mapping

Protection Mechanism Failure

Protection Mechanism Failure represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs