CVE-2026-72530: TrueConf Server

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

Yes, if you run TrueConf Server. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-08-20, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-09-03; treat that as the outer limit, not the target.
EPSS 1.7%, percentile 77: FIRST’s model estimates a 1.7% chance of exploitation activity in the next 30 days, higher than 77% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
Editorial verdict: Check exposure. TrueConf Server: Exploited Pre-Auth RCE Chain on Port 4307 — Only organizations that run TrueConf Server, or whose staff join meetings on other companies' TrueConf servers, are exposed; for them an unpatched, reachable server should be treated as compromised, because the chain is unauthenticated, yields SYSTEM and was used to infect the server's own users.

What it is

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.

CISA’s summary

TrueConf Server contains a code injection vulnerability that could allow an unauthorized remote attacker with network access via port 4307/TCP to use a specially crafted script to break out of the isolated environment and execute arbitrary code on the host system.

Weakness type: CWE-94.

Product: TrueConf Server · Assigned by: Kaspersky · Published: 2026-08-19

Affected and fixed versions

Vendor	Product	Affected versions (per CVE record)
TrueConf	TrueConf Server	< 5.3, 5.3 < 5.3.9, 5.4 < 5.4.9, 5.5 < 5.5.5

Severity scores

Scored by	CVSS	Score	Vector
Kaspersky	4.0	9.5 Critical	`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`
Kaspersky	3.1	9 Critical	`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H`

Attack vector: network (remotely reachable)
Attack complexity: high (needs special conditions)
Attack requirements: present (depends on deployment conditions)
Privileges required: none (no login)
User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

CISA KEV: added 2026-08-20; federal due date 2026-09-03. Known ransomware use: Unknown.
CISA 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.
CISA SSVC assessment: exploitation active, automatable no, technical impact total.
FIRST EPSS (model of 2026-10-21): 1.69% probability of exploitation activity in the next 30 days; percentile 77.

Timeline

2026-06-18 — erroneo.us brief: TrueConf Server: Exploited Pre-Auth RCE Chain on Port 4307
2026-08-19 — CVE record published by Kaspersky
2026-08-20 — Added to CISA’s Known Exploited Vulnerabilities catalog
2026-08-21 — CVE record last updated
2026-09-03 — CISA remediation deadline for US federal agencies

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Other references from the CVE record and advisory

securelist.com securelist.com

All exploited TrueConf vulnerabilities · Today’s Security Digest