# CVE-2021-42550: Deserialization of Untrusted Data in logback

Source: https://junglewise.ai/threats/cve-2021-42550-deserialization-of-untrusted-data-in-logback  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2021-12-17  
License: CC BY 4.0 with a link back

CVE-2021-42550 · Severity: low · CVSS 3.1 · Published 2021-12-17

Deserialization of Untrusted Data in logback

Technologies: [ch.qos.logback:logback-core (Maven)](https://junglewise.ai/threats/technologies/ch-qos-logback-logback-core). Vendors: [Maven](https://junglewise.ai/threats/vendors/maven).

## Quick answers

**Is CVE-2021-42550 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2021-42550 being exploited in the wild.

**How severe is CVE-2021-42550?** Low severity, with a CVSS score of 3.1, published 17 December 2021.

**Which products and versions are affected?** ch.qos.logback:logback-core (Maven) ECOSYSTEM:introduced=0,fixed=1.2.9.

**Is there a fix for CVE-2021-42550?** Yes. ch.qos.logback:logback-core (Maven): upgrade to 1.2.9 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2021-42550?** Check whether you run ch.qos.logback:logback-core (Maven) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- ch.qos.logback:logback-core (Maven): upgrade to 1.2.9 or later

  ```sh
  # set ch.qos.logback:logback-core to 1.2.9 in your pom.xml or build.gradle
  ```


## Affected products

- ch.qos.logback:logback-core (Maven) ECOSYSTEM:introduced=0,fixed=1.2.9

## Identifiers

- CVE-2021-42550
- GHSA-668q-qrv7-99fm

## Related threats

- [QOS.CH Sarl logback-core restricted deserialization in HardenedObjectInputStream](https://junglewise.ai/threats/cve-2026-10532-qos-ch-sarl-logback-core-restricted-deserialization-in)
- [QOS.CH logback-core deserialization bypass in HardenedObjectInputStream](https://junglewise.ai/threats/cve-2026-9828-qos-ch-logback-core-deserialization-bypass-in)
- [Logback allows an attacker to instantiate classes already present on the class path](https://junglewise.ai/threats/cve-2026-1225-logback-allows-an-attacker-to-instantiate-classes-already-present)
- [QOS.CH Logback-core code execution in conditional configuration processing](https://junglewise.ai/threats/cve-2025-11226-qos-ch-logback-core-code-execution-in-conditional-configuration)
- [QOS.CH logback-core Expression Language Injection vulnerability](https://junglewise.ai/threats/cve-2024-12798-qos-ch-logback-core-expression-language-injection-vulnerability)