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CVE Record

CVE-2026-4700: Mitigation bypass in the Networking: HTTP component

Mitigation bypass in the Networking: HTTP component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

CriticalCVSS 9.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

CVE-2026-4700 is a critical Mozilla Networking: HTTP mitigation bypass. The public record says it is fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9. Its score indicates possible full confidentiality, integrity, and availability impact, but the bundle does not describe the precise attack path.

Executive priority

Treat as urgent patch management for browser and mail fleets. The score is critical and the component processes network content, but available sources do not show active exploitation. Prioritize rapid updates and exception tracking over emergency incident response unless new evidence emerges.

Technical view

The CVE maps to CWE-288 and CWE-444, indicating an HTTP-related mitigation bypass or parsing inconsistency class. CVSS 3.1 is 9.8: network reachable, low complexity, no privileges, no user interaction, unchanged scope, and high CIA impact. Public detail in the bundle is limited to affected component and fixed versions.

Likely exposure

Exposure is most likely on endpoints or managed systems running Firefox, Firefox ESR, Thunderbird, or distro-packaged Mozilla builds below the fixed versions. Red Hat advisories and VEX data indicate downstream package tracking, but the bundle does not identify every affected Red Hat product version.

Exploitation context

No active exploitation is supported by the supplied evidence: KEV is false, and no cited source in the bundle claims exploitation in the wild. The high CVSS score means treat it as urgent even without confirmed exploitation.

Researcher notes

The source bundle is sparse: it names Networking: HTTP, CWE-288/CWE-444, fixed versions, and Red Hat tracking. It does not disclose root cause, affected request patterns, proof-of-concept status, or compensating controls. Avoid assuming exploitability details beyond the CVSS vector.

Mitigation direction

  • Upgrade Firefox to 149 or Firefox ESR 140.9 or later.
  • Upgrade Thunderbird to 149 or 140.9 or later.
  • Apply relevant Red Hat security advisories for managed Mozilla packages.
  • Check Mozilla and Red Hat guidance for deployment-specific mitigations.
  • Prioritize browser and mail clients that process untrusted HTTP content.

Validation and detection

  • Inventory Firefox, Firefox ESR, and Thunderbird versions across managed assets.
  • Confirm installed versions meet or exceed the fixed Mozilla releases.
  • Review Red Hat errata applicability for Linux-managed Mozilla packages.
  • Track the Mozilla Bugzilla entry for any newly public technical detail.
  • Document exceptions where endpoints cannot be updated immediately.
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-288: 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-444: 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
cve · low confidence lookup

CVE-2026-4700 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
34Source 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-2026-4700Attack 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: Mitigation bypass in the Networking: HTTP component
other:Red Hat severity ratingcvssV3_1
  • 2026-03-24T13:03:33.207Z: Reported to Red Hat.
  • 2026-03-24T12:30:28.913Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox140.9, 149Listed
MozillaThunderbird140.9, 149Listed
Weakness

CWE details

CWE-288CWE-444

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

CWE-288 · source CWE mapping

Authentication Bypass Using an Alternate Path or Channel

Authentication Bypass Using an Alternate Path or Channel represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-444 · source CWE mapping

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs