# 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.

- **Severity:** Low 2.9 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 May 2026
- **Updated:** 29 May 2026
- **Also known as:** CLEANSTART-2026-AE18231, CLEANSTART-2026-ET86830, CLEANSTART-2026-GP84897, CLEANSTART-2026-GS75454, CLEANSTART-2026-NU36119, DEBIAN-CVE-2026-9828, ECHO-7f02-286f-95bd, GHSA-p47f-322f-whfh, MINI-46mv-9pqv-4746, MINI-5ppj-v737-jc4v, MINI-5wmm-5jx4-5435, MINI-6849-8h6x-vmrx, MINI-6hm4-cj23-wx5x, MINI-8c8c-mvx2-fhmv, MINI-8m29-qmw2-qv65, MINI-8wg9-mqx6-gc3p, MINI-cgc3-f3pp-wf4x, MINI-f95m-x666-4hqj, MINI-fhhf-2c7r-99jm, MINI-fpqv-6mp9-4xm9, MINI-g78w-4xwq-w9g6, MINI-gvxh-x493-24fc, MINI-j47v-frmx-4f6r, MINI-ph9g-fc9m-fjv3, MINI-pjrr-9m6j-54ph, MINI-qr72-98wg-3c6r, MINI-r3hc-mh9v-f673, MINI-r6cv-95q4-c2q2, UBUNTU-CVE-2026-9828, openSUSE-SU-2026:11016-1

## 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 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-9828?

2 open source packages ship an affected version, including ch.qos.logback:logback-core.


| Package | Ecosystem | 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 |
| `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.

## Is CVE-2026-9828 being exploited?

There is no known exploitation of CVE-2026-9828 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-9828 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-9828 in the wild and no public exploit code.

Affected packages and fixed versions:
- ch.qos.logback:logback-core (Maven): affected all versions; fixed in 1.5.33
- ch.qos.logback:logback-core (Maven): affected all versions; fixed in 1.5.33

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-9828/ (Markdown: https://insights.sbomify.com/CVE-2026-9828/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-9828
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-9828
- OSV: https://osv.dev/vulnerability/CVE-2026-9828

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-9828/
Summaries are generated and may contain mistakes; the official description above is the record.