VDB-319863 · CVE-2025-8760 · MZ-25-03

INSTAR 2K+/4K 3.11.1 Build 1124 fcgi_server base64_decode Authorization buffer 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.
9.5	$0-$5k	0.00

Summaryinfo

A vulnerability was found in INSTAR 2K+ and 4K 3.11.1 Build 1124. It has been classified as critical. Impacted is the function base64_decode of the component fcgi_server. Performing a manipulation of the argument Authorization results in buffer overflow. This vulnerability was named CVE-2025-8760. The attack may be initiated remotely. There is no available exploit. It is suggested to use restrictive firewalling.

Detailsinfo

A vulnerability, which was classified as very critical, was found in INSTAR 2K+ and 4K 3.11.1 Build 1124. This affects the function base64_decode of the component fcgi_server. The manipulation of the argument Authorization with an unknown input leads to a buffer overflow vulnerability. CWE is classifying the issue as CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. This is going to have an impact on confidentiality, integrity, and availability.

The weakness was presented by Michael Imfeld with modzero AG as MZ-25-03. It is possible to read the advisory at modzero.com. This vulnerability is uniquely identified as CVE-2025-8760. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/13/2025).

It is possible to mitigate the weakness by firewalling .

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2025-24545). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

INSTAR

Name

Version

3.11.1 Build 1124

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 9.8
VulDB Meta Temp Score: 9.5

VulDB Base Score: 9.8
VulDB Temp Score: 9.2
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 9.8
CNA Vector: 🔒

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Buffer overflow
CWE: CWE-120 / 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

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Firewall
Status: 🔍

0-Day Time: 🔒

Timelineinfo

08/13/2025 Advisory disclosed
08/13/2025 +0 days VulDB entry created
08/13/2025 +0 days VulDB entry last update

Sourcesinfo

Advisory: MZ-25-03
Researcher: Michael Imfeld
Organization: modzero AG
Status: Not defined

CVE: CVE-2025-8760 (🔒)
GCVE (CVE): GCVE-0-2025-8760
GCVE (VulDB): GCVE-100-319863
EUVD: 🔒

Entryinfo

Created: 08/13/2025 08:16
Updated: 08/13/2025 09:44
Changes: 08/13/2025 08:16 (55), 08/13/2025 08:18 (2), 08/13/2025 09:21 (1), 08/13/2025 09:44 (30)
Complete: 🔍
Cache ID: 216::103