CVE-2026-110021Phoenix Contact PLCnext Engineer improper signature verification
CVE-2026-110021 is a improper signature verification in Phoenix Contact PLCnext Engineer, rated medium (6.9 on CVSS 4.0).
Why this priority: Medium severity, with no exploitation signal.
Published · Updated · NVD status: Received
What it is
A cryptographic signature is not checked properly, so forged data is accepted.
How it is reached
An attacker can exploit it by someone who can already run code or sign in on the machine, without an account, and nobody has to click anything.
What an attacker gains
A successful attack can change data or behaviour. In practice, this kind of flaw lets an attacker read or tamper with traffic, or pass a forged message as genuine.
Is it being exploited?
There is no public report of exploitation yet. EPSS estimates a 0.06% chance of exploitation activity in the next 30 days, higher than 0% of scored CVEs.
What to do
- Upgrade Phoenix Contact PLCnext Engineer to 2026.6 or later.
- Limit who can run code or sign in on the hosts that run it.
Description from NVD
PLCnext Engineer checks GSDX manifest reference digests but does not cryptographically verify the XML `SignatureValue` over canonicalized `SignedInfo`. An unauthenticated local attacker can modify signed GSDML content, update its manifest digest, retain the public certificate data, and leave an invalid nonempty `SignatureValue`. PLCnext Engineer prior to 2026.6 reports the package as `Valid` and selects the modified device description for import under the default policy.
What this means for your architecture.
A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.
Components it touches
- TLS termination and service-to-service channels. The flaw sits on the network path between clients and services.
- Signature checks. The flaw sits on the network path between clients and services.
Trust boundaries in play
- Host boundary. The attacker needs a foothold on the machine first; the flaw turns a small foothold into a bigger one.
- On the network path between clients and services. An attacker who crosses it can read or tamper with traffic, or pass a forged message as genuine.
Questions to answer about your own systems
- Where does Phoenix Contact PLCnext Engineer run in your systems, and at which version?
- Which of those hosts also run code or users you do not fully trust?
- What can it reach once compromised: which data stores, secrets and services?
Sources
- CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
- Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
- Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
- Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.