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CVE-2026-16396· NVD / CVE Program· CNA mozilla

Privilege escalation in WebExtensions

Privilege escalation in WebExtensions. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

HighCVSS 8.8 · v3.1—No exploit Fix available
Published
Jul 21, 2026
Updated
Jul 24, 2026
EPSS
0.2% · 14th percentile
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Report tools

JSON

Action score

35

Monitor

Low priority for now.

CVSS
35 / 40 · 8.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

Affected systems

VendorProduct
mozillafirefox
mozillathunderbird

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • mozilla firefoxbefore 140.13.0
  • mozilla firefoxbefore 153.0.0
  • mozilla thunderbirdbefore 140.13.0
  • mozilla thunderbird141.0 and later · before 153.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (mozilla). Independent of NVD's CPE analysis and usually ahead of it.

  • Mozilla Firefox

    • 140.13 and later · up to and including 140.*not affected · rpm
    • 153 and laternot affected · rpm

  • Mozilla Thunderbird

    • 140.13 and later · up to and including 140.*not affected · rpm
    • 153 and laternot affected · rpm

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12firefox-esrbefore 140.13.0esr-1~deb12u1140.13.0esr-1~deb12u1
Debian:12thunderbirdbefore 1:140.13.0esr-2~deb12u11:140.13.0esr-2~deb12u1
Debian:13firefox-esrbefore 140.13.0esr-1~deb13u1140.13.0esr-1~deb13u1
Debian:13thunderbirdbefore 1:140.13.0esr-2~deb13u11:140.13.0esr-2~deb13u1
Debian:14firefox-esrbefore 140.13.0esr-1140.13.0esr-1
Debian:14thunderbirdbefore 1:140.13.0esr-11:140.13.0esr-1

Same product

mozilla: all records

Other highest-scoring records for the same primary product.

  • CVE-2010-3765Mozilla Firefox 3.5.x through 3.5.14 and 3.6.x through 3.6.11, Thunderbird 3.1.6 before 3.1.6 and 3.0.x before 3.0.10, and SeaMonkey 2.x befKEV
    94Now
  • CVE-2019-11708Insufficient vetting of parameters passed with the Prompt:Open IPC message between child and parent processes can result in the non-sandboxeKEV
    87Now
  • CVE-2015-4495The PDF reader in Mozilla Firefox before 39.0.3, Firefox ESR 38.x before 38.1.1, and Firefox OS before 2.2 allows remote attackers to bypassKEV
    86Now
  • CVE-2013-1690Mozilla Firefox before 22.0, Firefox ESR 17.x before 17.0.7, Thunderbird before 17.0.7, and Thunderbird ESR 17.x before 17.0.7 do not properKEV
    86Now
  • CVE-2019-17026Incorrect alias information in IonMonkey JIT compiler for setting array elements could lead to a type confusion.KEV
    79This week
  • CVE-2024-9680An attacker was able to achieve code execution in the content process by exploiting a use-after-free in Animation timelines.KEV
    76This week

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:firefox-esr140.13.0esr-1~deb12u1 · Debian:12Package registry (OSV)
debian:thunderbird1:140.13.0esr-2~deb12u1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-7498528 days apartPrivilege escalation in the Enterprise Policies component
    39Monitor
  • CVE-2026-2777147 days apartPrivilege escalation in the Messaging System component
    39Monitor
  • CVE-2026-2780147 days apartPrivilege escalation in the Netmonitor component
    39Monitor
  • CVE-2026-2782147 days apartPrivilege escalation in the Netmonitor component
    39Monitor
  • CVE-2026-163710 days apartPrivilege escalation in the DOM: Navigation component
    35Monitor
  • CVE-2026-164010 days apartPrivilege escalation in the Data Loss Prevention component
    35Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-269 · Improper Privilege Management

CVSS vector

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

nvd-secondary

Root cause

To simplify setup, a service account is granted broad, cluster-wide permissions. The principle of least privilege is skipped during installation.

The bug in code

The whole CWE-269 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

yaml
kind: ClusterRolerules:  - apiGroups: ["*"]    resources: ["*"]    verbs: ["*"]

Fixed

yaml
kind: Rolemetadata:  namespace: lodos-systemrules:  - apiGroups: ["apps"]    resources: ["deployments"]    verbs: ["get", "list", "update"]

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

We use this product, ask for help

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records