Vulnary
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Critical· 9.8official fix available

CVE-2026-16363

CVE-2026-16363 is a critical vulnerability in JavaScript: WebAssembly's JIT compiler that could allow attackers to execute arbitrary code. It was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

publishedJul 21, 2026
last modifiedJul 24, 2026
sourcesNVD
severity · cvss
9.8
critical · how bad it is
exploitation · epss
<1%
36th percentile · chance of exploitation in 30 days
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →
auto-deletes from the system
counting…on Aug 22, 2026

An official fix is available, so this entry is kept for 30 days and then removed automatically.

01

Who is affected

Users of Firefox, Firefox ESR, Thunderbird, or Thunderbird ESR versions prior to the specified patches.

02

Real-world impact

Attackers could exploit this to run malicious code on affected systems, potentially leading to data theft or system compromise.

03

Why this severity

CVSS 9.8 (critical): High confidence in exploitability and severe impact on confidentiality, integrity, and availability.

04

What to do about it

official fix available
recommended steps
  1. 01Upgrade Firefox to version 153 or later.
  2. 02Upgrade Firefox ESR to version 140.13 or later.
  3. 03Upgrade Thunderbird to version 153 or later.
  4. 04Upgrade Thunderbird ESR to version 140.13 or later.

NVD description citing vendor patch versions

05

Timeline

  1. Jul 21, 2026 · 12d ago
    Published
    Disclosed and added to the National Vulnerability Database.
  2. Jul 23, 2026 · 10d ago
    Official fix available
    A vendor patch or mitigation now exists — see the remediation steps above.
  3. Jul 24, 2026 · 9d ago
    Advisory updated
    The NVD record was last revised.
06

How it’s attacked

Attack vectorNetwork (remote)
Attack complexityLow
Privileges requiredNone
User interactionNone needed
ScopeUnchanged
Confidentiality impactHigh
Integrity impactHigh
Availability impactHigh
07

References & advisories

NVD advisory ↗Search advisories ↗
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →