How severe is CVE-2021-34580?

CVE-2021-34580 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-34580 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (59th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-34580?

CVE-2021-34580 primarily affects Mbconnectline Mbconnect24. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-34580?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-34580 published?

CVE-2021-34580 was published on 2021-10-27 and last updated on 2026-06-17.

CVE-2021-34580

CVE-2021-34580 is a high-severity vulnerability in Mbconnectline Mbconnect24 with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-203.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 1% (59th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-203
Affected product: Mbconnectline Mbconnect24
Published: 2021-10-27
Last modified: 2026-06-17

Description

In mymbCONNECT24, mbCONNECT24 <= 2.9.0 an unauthenticated user can enumerate valid backend users by checking what kind of response the server sends for crafted invalid login attempts.

Frequently asked questions

What is CVE-2021-34580?: In mymbCONNECT24, mbCONNECT24 <= 2.9.0 an unauthenticated user can enumerate valid backend users by checking what kind of response the server sends for crafted invalid login attempts.
How severe is CVE-2021-34580?: CVE-2021-34580 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-34580 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (59th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-34580?: CVE-2021-34580 primarily affects Mbconnectline Mbconnect24. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-34580?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-34580 published?: CVE-2021-34580 was published on 2021-10-27 and last updated on 2026-06-17.

References

https://cert.vde.com/en/advisories/VDE-2021-037/

Affected products (2)

cpe:2.3:a:mbconnectline:mbconnect24:*:*:*:*:*:*:*:*
cpe:2.3:a:mbconnectline:mymbconnect24:*:*:*:*:*:*:*:*

More vulnerabilities in Mbconnectline Mbconnect24

CVE-2020-35565 — Critical (CVSS 9.8): An issue was discovered in MB CONNECT LINE mymbCONNECT24 and mbCONNECT24 through 2.6.2. The login pages bruteforce…
CVE-2020-10383 — Critical (CVSS 9.8): An issue was discovered in the MB CONNECT LINE mymbCONNECT24 and mbCONNECT24 software in all versions through 2.5.0.…
CVE-2026-33615 — Critical (CVSS 9.1): An unauthenticated remote attacker can exploit an unauthenticated SQL Injection vulnerability in the setinfo endpoint…
CVE-2023-0985 — High (CVSS 8.8): An Authorization Bypass vulnerability was found in MB Connect Lines mbCONNECT24, mymbCONNECT24 and Helmholz' myREX24…
CVE-2020-10382 — High (CVSS 8.8): An issue was discovered in the MB CONNECT LINE mymbCONNECT24 and mbCONNECT24 software in all versions through 2.5.0.…
CVE-2024-45273 — High (CVSS 8.4): An unauthenticated local attacker can decrypt the devices config file and therefore compromise the device due to a weak…

All CVEs affecting Mbconnectline Mbconnect24 →

Other CWE-203 (Observable Discrepancy) vulnerabilities

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CVE-2024-25714 — Critical (CVSS 9.8): In Rhonabwy through 1.1.13, HMAC signature verification uses a strcmp function that is vulnerable to side-channel…
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Browse all CWE-203 (Observable Discrepancy) vulnerabilities →