INSTAR 2K+/4K fcgi_server base64_decode buffer overflow

published 2025-08-13 last yr. modified 2026-06-17 4mo ago also EUVD-2025-24545

cvss: 9.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.9%; EPSS 0.9% chance of exploitation in 30 days, percentile 59%
public exploits: 0; none known

A vulnerability was identified 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 leads to buffer overflow. It is possible to initiate the attack remotely.

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CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: total
Assessed: last yr. (2025-08-13)

Exploit prediction

0.87% chance of exploitation in the next 30 days, higher than 59% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
CNA	4.0	9.3	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X
CNA	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:X/RL:W/RC:R
CNA	3.0	9.8	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:X/RL:W/RC:R
CNA	2.0	10.0	AV:N/AC:L/Au:N/C:C/I:C/A:C/E:ND/RL:W/RC:UR
CNA	4.0	9.3	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CNA	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA	2.0	10.0	AV:N/AC:L/Au:N/C:C/I:C/A:C

Affected products

INSTAR 2K+
INSTAR 4K

Classification

Weakness

CWE-120 Buffer Copy without Checking Size of Input
CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer

References

vuldb.com /?id.319863
vdb-entry, technical-description
vuldb.com /?ctiid.319863
signature, permissions-required
modzero.com /static/MZ-25-03_modzero_INSTAR.pdf
related

Sources

CVE List CVE-2025-8760
NVD CVE-2025-8760

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