How severe is CVE-2021-42550?

CVE-2021-42550 has a CVSS 3.x base score of 6.6, rated medium severity. It is exploitable over network with high attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-42550 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (90th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-42550?

CVE-2021-42550 primarily affects Qos Logback. In total, 17 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-42550?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-42550 published?

CVE-2021-42550 was published on 2021-12-16 and last updated on 2026-06-17.

CVE-2021-42550

CVE-2021-42550 is a medium-severity vulnerability in Qos Logback with a CVSS 3.x base score of 6.6. 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-502.

Key facts

Severity: Medium (CVSS 3.x base score 6.6)
CVSS v2: 8.5
EPSS exploit prediction: 4% (90th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-502
Affected product: Qos Logback
Published: 2021-12-16
Last modified: 2026-06-17

Description

In logback version 1.2.7 and prior versions, an attacker with the required privileges to edit configurations files could craft a malicious configuration allowing to execute arbitrary code loaded from LDAP servers.

Frequently asked questions

What is CVE-2021-42550?: In logback version 1.2.7 and prior versions, an attacker with the required privileges to edit configurations files could craft a malicious configuration allowing to execute arbitrary code loaded from LDAP servers.
How severe is CVE-2021-42550?: CVE-2021-42550 has a CVSS 3.x base score of 6.6, rated medium severity. It is exploitable over network with high attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-42550 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (90th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-42550?: CVE-2021-42550 primarily affects Qos Logback. In total, 17 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-42550?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-42550 published?: CVE-2021-42550 was published on 2021-12-16 and last updated on 2026-06-17.

References

Affected products (17)

cpe:2.3:a:qos:logback:*:*:*:*:*:*:*:*
cpe:2.3:a:qos:logback:1.3.0:alpha0:*:*:*:*:*:*
cpe:2.3:a:qos:logback:1.3.0:alpha1:*:*:*:*:*:*
cpe:2.3:a:qos:logback:1.3.0:alpha10:*:*:*:*:*:*
cpe:2.3:a:qos:logback:1.3.0:alpha2:*:*:*:*:*:*
cpe:2.3:a:qos:logback:1.3.0:alpha3:*:*:*:*:*:*
cpe:2.3:a:qos:logback:1.3.0:alpha4:*:*:*:*:*:*
cpe:2.3:a:qos:logback:1.3.0:alpha5:*:*:*:*:*:*
cpe:2.3:a:qos:logback:1.3.0:alpha6:*:*:*:*:*:*
cpe:2.3:a:qos:logback:1.3.0:alpha7:*:*:*:*:*:*
cpe:2.3:a:qos:logback:1.3.0:alpha8:*:*:*:*:*:*
cpe:2.3:a:qos:logback:1.3.0:alpha9:*:*:*:*:*:*
cpe:2.3:a:redhat:satellite:6.0:*:*:*:*:*:*:*
cpe:2.3:a:netapp:cloud_manager:-:*:*:*:*:*:*:*
cpe:2.3:a:netapp:service_level_manager:-:*:*:*:*:*:*:*
cpe:2.3:a:netapp:snap_creator_framework:-:*:*:*:*:*:*:*
cpe:2.3:a:siemens:sinec_nms:*:*:*:*:*:*:*:*

More vulnerabilities in Qos Logback

CVE-2017-5929 — Critical (CVSS 9.8): QOS.ch Logback before 1.2.0 has a serialization vulnerability affecting the SocketServer and ServerSocketReceiver…
CVE-2023-6481 — High (CVSS 7.1): A serialization vulnerability in logback receiver component part of logback version 1.4.13, 1.3.13 and 1.2.12 allows…
CVE-2023-6378 — High (CVSS 7.1): A serialization vulnerability in logback receiver component part of logback version 1.4.11 allows an attacker to mount…

All CVEs affecting Qos Logback →

Other CWE-502 (Deserialization of Untrusted Data) vulnerabilities

CVE-2026-41104 — Critical (CVSS 10.0): Deserialization of untrusted data in Microsoft Planetary Computer Pro allows an unauthorized attacker to disclose…
CVE-2026-43633 — Critical (CVSS 10.0): HestiaCP versions 1.9.0 through 1.9.4 contain a deserialization vulnerability in the web terminal component caused by a…
CVE-2026-33819 — Critical (CVSS 10.0): Deserialization of untrusted data in Microsoft Bing allows an unauthorized attacker to execute code over a network.
CVE-2026-20131 — Critical (CVSS 10.0): A vulnerability in the web-based management interface of Cisco Secure Firewall Management Center (FMC) Software could…
CVE-2026-25632 — Critical (CVSS 10.0): EPyT-Flow is a Python package designed for the easy generation of hydraulic and water quality scenario data of water…
CVE-2025-14931 — Critical (CVSS 10.0): Hugging Face smolagents Remote Python Executor Deserialization of Untrusted Data Remote Code Execution Vulnerability.…

Browse all CWE-502 (Deserialization of Untrusted Data) vulnerabilities →