CVE-2026-9828: QOS.CH logback-core deserialization bypass in HardenedObjectInputStream

CVE-2026-9828 · Severity: medium · CVSS 4 · Published 2026-05-28

Logback is a widely used logging framework for Java applications. A security flaw was identified where the component responsible for receiving log data over a network (SimpleSocketServer) does not sufficiently restrict the types of data it processes. While the risk is considered low because the system already has significant protections in place, a sophisticated attacker could potentially bypass these restrictions to manipulate internal application objects.

Technologies: ch.qos.logback:logback-core (Maven), QOS.CH Sarl Logback-Core. Vendors: Maven, QOS.CH Sarl.

Quick answers

Is CVE-2026-9828 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-9828 being exploited in the wild.
How severe is CVE-2026-9828?
Medium severity, with a CVSS score of 4, published 28 May 2026.
Which products and versions are affected?
ch.qos.logback:logback-core (Maven) <= 1.5.32, ECOSYSTEM:introduced=0,fixed=1.5.33; QOS.CH Sarl Logback-Core <= 1.5.32, through 1.5.32 inclusive.
Is there a fix for CVE-2026-9828?
Yes. ch.qos.logback:logback-core (Maven): upgrade to 1.5.33 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-9828 attacked?
It is attacked over the network or with local access, in a software library.
Am I affected by CVE-2026-9828?
Check whether you run ch.qos.logback:logback-core (Maven) or QOS.CH Sarl Logback-Core 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 1.5.33 or later
    # set ch.qos.logback:logback-core to 1.5.33 in your pom.xml or build.gradle

Technical details

A deserialization vulnerability exists in the HardenedObjectInputStream module of logback-core. An attacker who can influence serialized data sent to SimpleSocketServer or SimpleSSLSocketServer can bypass existing security restrictions to instantiate objects from the java.lang and java.util packages that are not explicitly blocked. While the HardenedObjectInputStream significantly limits the attack surface, making remote code execution (RCE) or privilege escalation difficult to achieve, it represents a bypass of intended security controls. The issue is addressed in version 1.5.33 by further hardening the deserialization whitelist.

Affected products

  • QOS.CH Sarl logback-core <= 1.5.32

Identifiers

  • CVE-2026-9828
  • GHSA-p47f-322f-whfh

Timeline

  • 2026-05-27: patched: Release of version 1.5.33
  • 2026-05-28: advisory: GitHub Advisory and NVD publication

References

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