CVE-2026-9828 Logback deserialization whitelist bypass for java.lang and java.util
Attackers can bypass deserialization restrictions in Logback to instantiate restricted Java classes, though remote code execution is not currently identified.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-9828?
CVE-2026-9828 is a low-severity unsafe deserialization vulnerability in QOS.CH Sarl logback, published on 28 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Deserialization of untrusted data vulnerability in QOS.CH Sarl logback logback-core (HardenedObjectInputStream (logback-core) modules) allows Object Injection albeit heavily restricted.
More precisely, an attacker able to influence serialized data sent to SimpleSocketServer or SimpleSSLSocketServer can instantiate objects from classes in the java.lang and java.util packages that are not explicitly blocked.
Although deserialization is heavily restricted by HardenedObjectInputStream and no practical way to achieve remote code execution or significant privilege escalation has been identified, this issue constitutes a bypass of the intended security restrictions.
This issue affects logback: through 1.5.32 inclusive.
Weakness: CWE-502
Which versions are affected by CVE-2026-9828?
2 open source packages ship an affected version, including ch.qos.logback:logback-core.
| Package | Affected | Fixed in |
|---|---|---|
ch.qos.logback:logback-core Maven | All versions | 1.5.33 |
ch.qos.logback:logback-core Maven | All versions | 1.5.33 |
Linux distribution packages (1)
logback openSUSE:Tumbleweed | All versions | 1.5.34-2.1 |
How do I fix CVE-2026-9828?
Upgrade ch.qos.logback:logback-core to 1.5.33 or later.
Upgrade, and only deserialise data from trusted sources or with an allow-list of types. More about Unsafe deserialization.
Is CVE-2026-9828 being exploited?
There is no known exploitation of CVE-2026-9828 in the wild and no public exploit code.
Sources
Also known as CLEANSTART-2026-AE18231, CLEANSTART-2026-ET86830, CLEANSTART-2026-GP84897, CLEANSTART-2026-GS75454, CLEANSTART-2026-NU36119, DEBIAN-CVE-2026-9828 and 24 more.