CVE
An attacker who gains the ability to execute arbitrary code on a system with TrueConf Server (Linux) versions from 4.7.2 up to, but not…
Affects TrueConf Server (Linux) versions 4.7.2 up to, but not including, 5.5.6, and only where an attacker can already run code as the trueconf user. Fixed in 5.5.6.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 5.5.6
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. TrueConf Server (Linux) versions from 4.7.2 up to, but not including, 5.5.6 installed Attacker must already be able to execute arbitrary code as the user trueconf, by exploiting some other vulnerability
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 15/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: no
- Technical impact: total
Summary
An attacker who gains the ability to execute arbitrary code on a system with TrueConf Server (Linux) versions from 4.7.2 up to, but not including, 5.5.6 installed, running as the user trueconf (by exploiting some other vulnerability), can elevate their privileges to root.
Who should check
Teams running TrueConf Server (Linux) versions 4.7.2 up to 5.5.6, excluding 5.5.6 itself
Read the source excerpt
“All versions from 4.7.2 up to, but not including, 5.5.6”
cve.now Index
- Exploitation0/40No signal
- Exposure5/25Specific setups only
- Reach?/20Unknown. No tracked technology or package matched
- Severity9.5/10CVSS 8.5, total technical impact per CISA
- No patch0/5No signal
What would change the score
- Would score about 65 if added to CISA KEV
- Would score about 60 if CISA's SSVC rates exploitation active
- Would score about 25 if CISA's SSVC rates it automatable
What to do
Check whether your setup matches what the bug needs.
TrueConf Server (Linux) versions from 4.7.2 up to, but not including, 5.5.6 installed Attacker must already be able to execute arbitrary code as the user trueconf, by exploiting some other vulnerabilityUpgrade to a fixed version: 5.5.6.
Workaround: Perform a full check with anti-virus software that has up-to-date anti-virus databases and software modules.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-123040 (An attacker who gains the ability to execute arbitrary code on a system with TrueConf Server (Linux) versions from 4.7.2 up to, but not…), using the cve.now data below.
Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.
What cve.now has for CVE-2026-123040 (entry last updated 2026-11-11):
Affected:
- TrueConf TrueConf Server: from 4.7.2, fixed in 5.5.6
Fixed versions: 5.5.6.
Conditions (all must be true for the bug to be hit):
- TrueConf Server (Linux) versions from 4.7.2 up to, but not including, 5.5.6 installed (source: https://ics-cert.kaspersky.com/advisories/2026/11/10/trueconf-server-linux-incorrect-default-permissions/)
- Attacker must already be able to execute arbitrary code as the user trueconf, by exploiting some other vulnerability (source: https://ics-cert.kaspersky.com/advisories/2026/11/10/trueconf-server-linux-incorrect-default-permissions/)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: local access, low-privilege login, no user action.
Workaround: Perform a full check with anti-virus software that has up-to-date anti-virus databases and software modules. (source: https://www.cve.org/CVERecord?id=CVE-2026-123040)
CISA KEV: CVE-2026-123040 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-123040 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://ics-cert.kaspersky.com/advisories/2026/11/10/trueconf-server-linux-incorrect-default-permissions/
- https://www.cve.org/CVERecord?id=CVE-2026-123040
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-123040
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-123040"}.Timeline
- CVE published
- First seen by cve.now
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: total
- Record last updated
Affected versions
- TrueConf TrueConf Server
From 4.7.2 · fixed in 5.5.6
Evidence 3
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-123040
Is CVE-2026-123040 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
A local attacker who can already run code as the trueconf user can raise their privileges to root. The bug is a local privilege escalation, not a remote one.Source: ics-cert.kaspersky.com, cve.org
Which versions are affected by CVE-2026-123040?
TrueConf Server: from 4.7.2 before 5.5.6.Source: cve.now feed data
Am I affected, and how do I check?
TrueConf Server (Linux) versions from 4.7.2 up to, but not including, 5.5.6 are in scope. Check the installed TrueConf Server version on the Linux system against that range.Source: ics-cert.kaspersky.com, cve.org
How do I fix CVE-2026-123040?
Update TrueConf Server (Linux) to version 5.5.6 or newer.Source: ics-cert.kaspersky.com, cve.org