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NVD / CVE Program· CNA CERTVDE

CVE-2021-33540: Phoenix Contact: Undocumented FTP acces in certain AXL F BK and IL BK devices

Noroxi assessment

Priority: Monitor (action score 29/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.72% (FIRST EPSS); higher than 54.2% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to the record, no fixed version is available yet.

Low priority for now. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In certain devices of the Phoenix Contact AXL F BK and IL BK product families an undocumented password protected FTP access to the root directory exists.

HighCVSS 7.3 · v3.1—No exploit No fix recorded
Published
Jun 25, 2021
Updated
Jun 16, 2026
EPSS
0.7% · 54th percentile

Report tools

JSON

Action score

29

Monitor

Low priority for now.

CVSS
29 / 40 · 7.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.7%

CNA vs NVD score

NVD
7.3
CNA · CERTVDE
7.3
agree

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-33540

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
phoenixcontactaxl f bk pn tps xc firmware
phoenixcontactaxl f bk pn tps xc
phoenixcontactaxl f bk pn tps firmware
phoenixcontactaxl f bk pn tps
phoenixcontactaxl f bk eip firmware
phoenixcontactaxl f bk eip
phoenixcontactaxl f bk eip ef firmware
phoenixcontactaxl f bk eip ef
phoenixcontactaxl f bk eth firmware
phoenixcontactaxl f bk eth
phoenixcontactaxl f bk eth xc firmware
phoenixcontactaxl f bk eth xc

and 24 more

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • phoenixcontact axl f bk eip ef firmwarebefore 1.30
  • phoenixcontact axl f bk eip firmwarebefore 1.30
  • phoenixcontact axl f bk eth firmwarebefore 1.30
  • phoenixcontact axl f bk eth net2 firmwareall versions
  • phoenixcontact axl f bk eth xc firmwarebefore 1.30
  • phoenixcontact axl f bk pn firmwareall versions
  • phoenixcontact axl f bk pn tps firmwarebefore 1.30
  • phoenixcontact axl f bk pn tps xc firmwarebefore 1.30
  • phoenixcontact axl f bk pn xc firmwareall versions
  • phoenixcontact axl f bk s35 firmwarebefore 1.40
  • phoenixcontact axl f bk sas firmwareall versions
  • phoenixcontact il eip bk di8 do4 2tx-pac firmwareall versions
  • phoenixcontact il eth bk di8 do4 2tx-pac firmwareall versions
  • phoenixcontact il eth bk di8 do4 2tx-xc-pac firmwareall versions
  • phoenixcontact il pn bk di8 do4 2scrj-pac firmwareall versions
  • phoenixcontact il pn bk di8 do4 2tx-pac firmwareall versions
  • phoenixcontact il pn bk-pac firmwareall versions
  • phoenixcontact il s3 bk di8 do4 2tx-pac firmwareall versions

Versions reported by the vendor

Affected version ranges reported by the assigning authority (CERTVDE). Independent of NVD's CPE analysis and usually ahead of it.

  • Phoenix Contact AXL F BK

    • AXL F PN (2701815) all revisions, AXL F PN XC (2701222) all revisions, AXL F ETH NET2 (2702177) all revisions, AXL F SAS (2701457) all revisionsaffected
    • AXL F PN TPS XC (1068857) and later · before 1.30affected
    • AXL F EIP EF (2702782) and later · before 1.30affected
    • AXL F PN TPS (2403869) and later · before 1.30affected
    • AXL F EIP (2688394) and later · before 1.30affected
    • AXL F ETH (2688459) and later · before 1.30affected
    • AXL F ETH XC (2701949) and later · before 1.30affected
    • AXL F S3 (2701686) and later · before 1.40affected

  • Phoenix Contact IL

    • IL PN BK-PAC (2403696) all revisions, IL PN BK DI8 DO4 2TX-PAC (2703994) all revisions, IL PN BK DI8 DO4 2SCRJ-PAC (2878379) all revisions, IL ETH BK DI8 DO4 2TX-XC-PAC (2701388) all revisions, IL ETH BK DI8 DO4 2TX-PAC (2703981) all revisions, IL EIP BK DI8 DO4 2TX-PAC (2897758) all revisions, IL S3 BK DI8 DO4 2TX-PAC (2692380) all revisionsaffected

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
low · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
Low
Integrity impact
Low
Availability impact
Low

Weakness class (CWE)

CWE-798 · Use of Hard-coded Credentials

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

nvd-primary

Root cause

For convenience in support or manufacturing, an account that is identical on every device is embedded in the software. Credentials learned from one device work on all of them.

The bug in code

The whole CWE-798 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

ts
const SUPPORT_USER = "support";const SUPPORT_PASS = "hardcoded-password";

Fixed

ts
const creds = await provisioning.deviceCredentials(deviceId);if (creds.mustRotate) await forcePasswordChange(deviceId);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records