Mozilla Firefox up to 115.41/140.16/153.3/156 Streams reliance on undefined, unspecified, or implementation-defined behavior

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
7.0$5k-$25k0.00

Summaryinfo

A vulnerability was found in Mozilla Firefox up to 115.41/140.16/153.3/156 and classified as critical. This issue affects some unknown processing of the component Streams. Such manipulation leads to reliance on undefined, unspecified, or implementation-defined behavior. This vulnerability is listed as CVE-2026-100771. The attack may be performed from remote. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Mozilla Firefox up to 115.41/140.16/153.3/156. Affected by this issue is an unknown code of the component Streams. The manipulation with an unknown input leads to a reliance on undefined, unspecified, or implementation-defined behavior vulnerability. Using CWE to declare the problem leads to CWE-758. The product uses an API function, data structure, or other entity in a way that relies on properties that are not always guaranteed to hold for that entity. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Undefined behavior in the DOM: Streams component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.

The advisory is available at bugzilla.mozilla.org. This vulnerability is handled as CVE-2026-100771 since 09/26/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $5k-$25k at the moment (estimation calculated on 10/13/2026).

The vulnerability scanner Nessus provides a plugin with the ID 365293 (Amazon Linux 2 : firefox (ALASFIREFOX-2026-066)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 115.42, 140.17, 153.4 or 157 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (365293) and CERT Bund (WID-SEC-2026-3654). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Affected

  • Debian Linux
  • Mozilla Firefox ESR
  • Mozilla Firefox
  • 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: 7.3
VulDB Meta Temp Score: 7.0

VulDB Base Score: 7.3
VulDB Temp Score: 7.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
💳💳💳💳💳💳
💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock

VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Reliance on undefined, unspecified, or implementation-defined behavior
CWE: CWE-758
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-DayUnlockUnlockUnlockUnlock
TodayUnlockUnlockUnlockUnlock

Nessus ID: 365293
Nessus Name: Amazon Linux 2 : firefox (ALASFIREFOX-2026-066)

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Firefox 115.42/140.17/153.4/157

Timelineinfo

09/26/2026 CVE reserved
09/29/2026 +3 days Advisory disclosed
09/29/2026 +0 days VulDB entry created
10/13/2026 +14 days VulDB entry last update

Sourcesinfo

Vendor: mozilla.org
Product: mozilla.org

Advisory: bugzilla.mozilla.org
Status: Confirmed

CVE: CVE-2026-100771 (🔒)
GCVE (CVE): GCVE-0-2026-100771
GCVE (VulDB): GCVE-100-411338
CERT Bund: WID-SEC-2026-3654 - Mozilla Firefox, Firefox ESR und Thunderbird: Mehrere Schwachstellen

Entryinfo

Created: 09/29/2026 15:12
Updated: 10/13/2026 07:22
Changes: 09/29/2026 15:12 (57), 10/03/2026 22:49 (7), 10/13/2026 07:22 (2)
Complete: 🔍
Cache ID: 216::103

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Discussion

No comments yet. Languages: en.

Please log in to comment.

◂ PreviousOverviewNext ▸

Do you need the next level of professionalism?

Upgrade your account now!