Vulnerability · Published May 28, 2026 · Assigned by NCSC.ch
CVE-2026-9828Logback deserialization whitelist bypass for java.lang and java.util
Low 2.9
In plain English
A low-severity unsafe deserialization in logback from QOS.CH Sarl. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 31% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | logback | no fix listed | DEBIAN-CVE-2026-9828 |
| Debian:13 | logback | no fix listed | DEBIAN-CVE-2026-9828 |
| Debian:14 | logback | 1:1.6.3-1 | DEBIAN-CVE-2026-9828 |
| Maven | ch.qos.logback:logback-core | 1.5.33 | GHSA-p47f-322f-whfh |
| Ubuntu:24.04:LTS | logback | no fix listed | UBUNTU-CVE-2026-9828 |
| Ubuntu:25.10 | logback | no fix listed | UBUNTU-CVE-2026-9828 |
| Ubuntu:26.04:LTS | logback | no fix listed | UBUNTU-CVE-2026-9828 |
| Ubuntu:26.10 | logback | no fix listed | UBUNTU-CVE-2026-9828 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| QOS.CH Sarl | logback | 0 – through 1.5.32 |
Weakness: CWE-502 · Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:P/RE:L/U:Green