Mozilla Firefox up to 115.5 nsTextFragment heap-based overflow

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.
7.4	$5k-$25k	0.00

Summaryinfo

A vulnerability identified as critical has been detected in Mozilla Firefox up to 115.5. The affected element is the function nsTextFragment. Performing a manipulation results in heap-based overflow. This vulnerability is reported as CVE-2023-6858. The attack is possible to be carried out remotely. No exploit exists. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Mozilla Firefox up to 115.5 (Web Browser). It has been classified as critical. This affects the function nsTextFragment. The manipulation with an unknown input leads to a heap-based overflow vulnerability. CWE is classifying the issue as CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

Firefox was susceptible to a heap buffer overflow in `nsTextFragment` due to insufficient OOM handling. This vulnerability affects Firefox ESR < 115.6, Thunderbird < 115.6, and Firefox < 121.

The weakness was disclosed 12/19/2023. The advisory is shared at mozilla.org. This vulnerability is uniquely identified as CVE-2023-6858 since 12/15/2023. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 05/08/2025).

The vulnerability scanner Nessus provides a plugin with the ID 214469 (Debian dla-3697 : firefox-esr - security update), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 115.6 eliminates this vulnerability. The upgrade is hosted for download at mozilla.org.

The vulnerability is also documented in the vulnerability database at Tenable (214469). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

Web Browser

Vendor

Mozilla

Name

Firefox

Version

License

open-source

Website

Vendor: https://www.mozilla.org/
Product: https://www.mozilla.org/en-US/firefox/

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.6
VulDB Meta Temp Score: 7.4

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

NVD Base Score: 8.8
NVD Vector: 🔍

CVSSv2info

AV	AC	Au	C	I	A
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💳	💳	💳	💳	💳	💳
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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

Exploitinginfo

Class: Heap-based overflow
CWE: CWE-122 / CWE-119
CAPEC: 🔍
ATT&CK: 🔍

Physical: No
Local: No
Remote: Yes

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Nessus ID: 214469
Nessus Name: Debian dla-3697 : firefox-esr - security update

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔍

Upgrade: Firefox 115.6

Timelineinfo

12/15/2023 🔍
12/19/2023 +4 days 🔍
12/19/2023 +0 days 🔍
05/08/2025 +506 days 🔍

Sourcesinfo

Vendor: mozilla.org
Product: mozilla.org

Advisory: DLA 3697-1
Status: Confirmed

CVE: CVE-2023-6858 (🔍)
GCVE (CVE): GCVE-0-2023-6858
GCVE (VulDB): GCVE-100-248397

Entryinfo

Created: 12/19/2023 16:38
Updated: 05/08/2025 04:53
Changes: 12/19/2023 16:38 (42), 01/12/2024 18:53 (1), 01/12/2024 19:00 (11), 01/22/2025 21:02 (17), 04/21/2025 00:43 (3), 05/08/2025 04:53 (1)
Complete: 🔍
Cache ID: 216::103

If you want to get the best quality for vulnerability data then you always have to consider VulDB.