Mozilla Firefox up to 115.35/140.10/150 WebIDL use after free

CVSS Meta Temp Score
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CTI Interest Score
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6.6$5k-$25k0.00

Summaryinfo

A vulnerability was found in Mozilla Firefox up to 115.35/140.10/150. It has been rated as critical. This issue affects some unknown processing of the component WebIDL. Performing a manipulation results in use after free. This vulnerability is known as CVE-2026-8947. Remote exploitation of the attack is possible. No exploit is available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability, which was classified as critical, was found in Mozilla Firefox up to 115.35/140.10/150. This affects an unknown function of the component WebIDL. The manipulation with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

Use-after-free in the DOM: Bindings (WebIDL) component. This vulnerability was fixed in Firefox 151, Firefox ESR 115.36, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

The advisory is shared at bugzilla.mozilla.org. This vulnerability is uniquely identified as CVE-2026-8947 since 05/19/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 06/17/2026).

The vulnerability scanner Nessus provides a plugin with the ID 315434 (Mozilla Thunderbird < 151.0), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 115.36, 140.11 or 151 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (315434), EUVD (EUVD-2026-30896) and CERT Bund (WID-SEC-2026-1606). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

  • Debian Linux
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • SUSE Linux
  • Oracle Linux
  • IGEL OS
  • SUSE openSUSE
  • RESF Rocky Linux
  • Mozilla Firefox
  • Mozilla Firefox ESR
  • Mozilla Thunderbird

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.8
VulDB Meta Temp Score: 6.6

VulDB Base Score: 6.3
VulDB Temp Score: 6.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

ADP CISA Base Score: 7.3
ADP CISA Vector: 🔒

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Use after free
CWE: CWE-416 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 315434
Nessus Name: Mozilla Thunderbird < 151.0

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Firefox 115.36/140.11/151

Timelineinfo

05/19/2026 Advisory disclosed
05/19/2026 +0 days CVE reserved
05/19/2026 +0 days VulDB entry created
06/17/2026 +29 days VulDB entry last update

Sourcesinfo

Vendor: mozilla.org
Product: mozilla.org

Advisory: bugzilla.mozilla.org
Status: Confirmed

CVE: CVE-2026-8947 (🔒)
GCVE (CVE): GCVE-0-2026-8947
GCVE (VulDB): GCVE-100-364665
EUVD: 🔒
CERT Bund: WID-SEC-2026-1606 - Mozilla Firefox und Thunderbird: Mehrere Schwachstellen

Entryinfo

Created: 05/19/2026 15:55
Updated: 06/17/2026 13:24
Changes: 05/19/2026 15:55 (56), 05/19/2026 17:59 (1), 05/20/2026 05:15 (2), 05/23/2026 11:52 (12), 05/27/2026 08:33 (7), 06/17/2026 13:24 (1)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Discussion

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