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

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.

Published: 2021-06-25 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-33540 is rated Moderate Risk (46.8/100): CVSS High severity, with low exploitation likelihood (EPSS 0.72%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-33540

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.24% 0.72% +0.49%
2 2025-03-17 0.08% 0.24% +0.16%
3 2023-03-07 — 0.08% —

Full EPSS history (7 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-33540

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.3 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 3.9 3.4 [email protected]
7.3 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 3.9 3.4 [email protected]
7.5 2.0 HIGH
AV:N/AC:L/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 6.4 [email protected]

Weakness enumeration for CVE-2021-33540

Affected software / configurations for CVE-2021-33540

Vendor Product Version Raw CPE
phoenixcontact axl_f_bk_pn_tps_xc_firmware < 1.30 cpe:2.3:o:phoenixcontact:axl_f_bk_pn_tps_xc_firmware:*:*:*:*:*:*:*:*
phoenixcontact axl_f_bk_pn_tps_firmware < 1.30 cpe:2.3:o:phoenixcontact:axl_f_bk_pn_tps_firmware:*:*:*:*:*:*:*:*
phoenixcontact axl_f_bk_eip_firmware < 1.30 cpe:2.3:o:phoenixcontact:axl_f_bk_eip_firmware:*:*:*:*:*:*:*:*
phoenixcontact axl_f_bk_eip_ef_firmware < 1.30 cpe:2.3:o:phoenixcontact:axl_f_bk_eip_ef_firmware:*:*:*:*:*:*:*:*
phoenixcontact axl_f_bk_eth_firmware < 1.30 cpe:2.3:o:phoenixcontact:axl_f_bk_eth_firmware:*:*:*:*:*:*:*:*
phoenixcontact axl_f_bk_eth_xc_firmware < 1.30 cpe:2.3:o:phoenixcontact:axl_f_bk_eth_xc_firmware:*:*:*:*:*:*:*:*
phoenixcontact axl_f_bk_s35_firmware < 1.40 cpe:2.3:o:phoenixcontact:axl_f_bk_s35_firmware:*:*:*:*:*:*:*:*
phoenixcontact axl_f_bk_pn_firmware — cpe:2.3:o:phoenixcontact:axl_f_bk_pn_firmware:*:*:*:*:*:*:*:*
phoenixcontact axl_f_bk_pn_xc_firmware — cpe:2.3:o:phoenixcontact:axl_f_bk_pn_xc_firmware:*:*:*:*:*:*:*:*
phoenixcontact axl_f_bk_eth_net2_firmware — cpe:2.3:o:phoenixcontact:axl_f_bk_eth_net2_firmware:*:*:*:*:*:*:*:*
phoenixcontact axl_f_bk_sas_firmware — cpe:2.3:o:phoenixcontact:axl_f_bk_sas_firmware:*:*:*:*:*:*:*:*
phoenixcontact il_pn_bk-pac_firmware — cpe:2.3:o:phoenixcontact:il_pn_bk-pac_firmware:*:*:*:*:*:*:*:*
phoenixcontact il_pn_bk_di8_do4_2tx-pac_firmware — cpe:2.3:o:phoenixcontact:il_pn_bk_di8_do4_2tx-pac_firmware:*:*:*:*:*:*:*:*
phoenixcontact il_pn_bk_di8_do4_2scrj-pac_firmware — cpe:2.3:o:phoenixcontact:il_pn_bk_di8_do4_2scrj-pac_firmware:*:*:*:*:*:*:*:*
phoenixcontact il_eth_bk_di8_do4_2tx-xc-pac_firmware — cpe:2.3:o:phoenixcontact:il_eth_bk_di8_do4_2tx-xc-pac_firmware:*:*:*:*:*:*:*:*
phoenixcontact il_eth_bk_di8_do4_2tx-pac_firmware — cpe:2.3:o:phoenixcontact:il_eth_bk_di8_do4_2tx-pac_firmware:*:*:*:*:*:*:*:*
phoenixcontact il_eip_bk_di8_do4_2tx-pac_firmware — cpe:2.3:o:phoenixcontact:il_eip_bk_di8_do4_2tx-pac_firmware:*:*:*:*:*:*:*:*
phoenixcontact il_s3_bk_di8_do4_2tx-pac_firmware — cpe:2.3:o:phoenixcontact:il_s3_bk_di8_do4_2tx-pac_firmware:*:*:*:*:*:*:*:*

References for CVE-2021-33540

cvelogic Threat Intelligence