Description
A remote unauthorized attacker with network access via port 4307/TCP to the TrueConf server versions 5.3.X to 5.3.9, 5.4.X to 5.4.9, 5.5.X to 5.5.5, and earlier could use a specially crafted script to break out of the isolated environment and execute arbitrary code on the host system.
Description as published by the source, in English.
Key facts
Published
2026-08-19
Last modified
2026-08-21
Assigned by
vulnerability@kaspersky.com
CVSS vector
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/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:Scored by
vulnerability@kaspersky.com
Fix available
Not registered in the sources
Actively exploited
CISA added this vulnerability to the Known Exploited Vulnerabilities
catalogue on 2026-08-20,
with a remediation deadline of 2026-09-03 for US federal agencies.
Required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
Affected products
Vendor
Product
Versions
Status
Trueconf
Trueconf Server
< 5.3.9.10013
Affected
Trueconf
Trueconf Server
< 5.3.9.10015
Affected
Trueconf
Trueconf Server
≥ 5.4.0.12689, < 5.4.9.10072
Affected
Trueconf
Trueconf Server
≥ 5.4.0.12700, < 5.4.9.10019
Affected
Trueconf
Trueconf Server
≥ 5.5.0.13826, < 5.5.5.10010
Affected
Trueconf
Trueconf Server
≥ 5.5.0.13828, < 5.5.5.10009
Affected
Weakness type
Attack techniques
Derived through the weakness type: CVE to CWE to CAPEC to ATT&CK.
This shows which techniques the weakness class is historically used for.
It does not assert that this vulnerability has been exploited that way.
T1027.006 : HTML Smuggling stealth
T1027.009 : Embedded Payloads stealth
T1564.009 : Resource Forking stealth
References
Sources and freshness
CVE
i
CVE
Common Vulnerabilities and Exposures
×
What it is A reference number naming one specific vulnerability, for example CVE-2024-9474.
What it tells you Which vulnerability we are talking about, and in which product.
What it does NOT tell you Nothing about how serious it is, whether anyone is exploiting it, or whether it concerns you.
Why it matters Without a shared number, vendor, authority and tooling cannot discuss the same flaw.
Used with the others The number is the key. NVD, KEV and EPSS all describe the same CVE.
NVD
i
NVD
National Vulnerability Database
×
What it is A US register that fills in each CVE with structured detail.
What it tells you How serious the flaw is technically (CVSS, 0 to 10), and which versions are affected.
What it does NOT tell you Whether the vulnerability is actually being exploited, and how important the system is to your business.
Why it matters This is what decides whether your version is affected.
Used with the others CVSS says how bad it could get. KEV and EPSS say how likely it is to happen.
CWE
i
CWE
Common Weakness Enumeration
×
What it is A catalogue of kinds of mistakes, not individual flaws, such as "forgot to check the password".
What it tells you What kind of weakness lies behind the vulnerability.
What it does NOT tell you Anything about this vulnerability in your system. It describes the class, not the case.
Why it matters If the same mistake recurs at one vendor, that is a pattern to raise.
Used with the others CVE is the incident, CWE the type of cause. Use it to learn, not to triage.
CISA KEV
i
CISA KEV
Known Exploited Vulnerabilities
×
What it is A list from the US authorities of vulnerabilities observed in real attacks.
What it tells you That someone has actually used it against someone. No longer theory.
What it does NOT tell you Whether you are being attacked, or how much damage it would do to you.
Why it matters The strongest single signal there is: from "could happen" to "is happening".
Used with the others A KEV listing normally outweighs a high CVSS score on its own.
EPSS
i
EPSS
Exploit Prediction Scoring System
×
What it is A percentage estimate of how likely exploitation is within the next 30 days.
What it tells you How likely exploitation is, compared with every other known vulnerability.
What it does NOT tell you That it has happened (KEV answers that), or how much damage it does (CVSS).
Why it matters Most vulnerabilities are never exploited. EPSS separates out the few that will be.
Used with the others High EPSS plus KEV means urgency. High CVSS, low EPSS, unexposed can be scheduled.
How to read this together
No single value should be used on its own. A high CVSS score does not
mean a vulnerability is being exploited, and a low one does not mean it
is harmless. The four sources answer four different questions.
CVE names the specific vulnerability.NVD adds severity and technical detail about it.CWE describes the type of mistake behind it.CISA KEV shows that it is already being exploited.EPSS estimates how likely exploitation is soon.
The order that decides what is urgent
Do you actually have the product?
Is the version you run affected?
Is it listed in CISA KEV?
Does it have a high EPSS score?
Is the system reachable from the internet or from others?
How important is the system to the business?
Are there compensating controls already in place?
The first two questions are not about the vulnerability at all. They are
about you, and they remove most of the list before you start.
A short example
Fix this week
CVSS 6,5 (medium)
In CISA KEV: yes
EPSS: 94 per cent
A firewall facing the internet
Can be scheduled
CVSS 9,8 (critical)
In CISA KEV: no
EPSS: 0,04 per cent
A test server with no internet access
Sorted by CVSS alone, the one on the right comes first. It is the more
serious flaw in theory. But the one on the left is being used against
real organisations right now, and it sits where an attacker can reach
it. That is the one to fix first.
The critical one still has to be fixed. It just does not have to be
fixed today.
This product uses the NVD API but is not endorsed or certified by the NVD.
CVE and the CVE logo are registered trademarks of The MITRE Corporation;
CVE records are used under the CVE Terms of Use .
CWE is a trademark of The MITRE Corporation, used per the
CWE Terms of Use .
KEV data from CISA (CC0).
Exploitation probability from EPSS , a FIRST.org project.
Open-source package data from OSV and the
GitHub Advisory Database (CC-BY 4.0).
Scores and vectors are shown as published by the sources. The ordering of
results is Berigo's own editorial assessment, described on the search page,
and is not NVD data. An empty result never means a system is safe.
