# CVE-2026-110803: Session Lock Leak on an Invalid UI Id Allows Denial of Service in Vaadin Framework 8


- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 21 Oct 2026
- **Updated:** 21 Oct 2026

## What is CVE-2026-110803?

CVE-2026-110803 is a high-severity vulnerability in vaadin framework, published on 21 Oct 2026. 

### Official description

VaadinService.requestEnd() in Vaadin Framework 8 locks the session and then reads the v-uiId request parameter outside the block that releases the lock. A request carrying a non-numeric v-uiId makes Integer.parseInt throw while the session lock is held, so the lock is never released and the container thread returns to its pool still owning it. Every later request to that session then blocks forever in VaadinService.lockSession(), and repeating the request exhausts the thread pool and takes the application down. No authentication is required: a session cookie, which any client obtains with a single request, is enough. Vaadin 10 and later are not affected, because Flow releases the lock in a finally block and does not read that parameter there, and Vaadin Framework 7 is not affected either.

Users of affected versions should apply the following mitigation or upgrade. Releases that have fixed this issue include:

Product version
Vaadin Framework 8.16.0 - 8.32.1

Mitigation
Upgrade to 8.32.2

Vaadin Framework 7 and Vaadin 10 and later do not carry this behaviour and need no upgrade for this issue.

Artifacts
Maven coordinates / Vulnerable versions / Fixed version
com.vaadin:vaadin-server / 8.16.0 - 8.32.1 / >=8.32.2
com.vaadin:vaadin-server-mpr-jakarta / 8.18.0 - 8.32.1 / >=8.32.2

Weakness: CWE-667 (Improper Locking), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-110803?


## How do I fix CVE-2026-110803?

No fix has been published for CVE-2026-110803 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-110803 being exploited?

There is no known exploitation of CVE-2026-110803 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-110803 and fix it if it is affected.

What it is: CVE-2026-110803 is a high-severity vulnerability in vaadin framework, published on 21 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-110803 in the wild and no public exploit code.

Affected product: vaadin framework. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-110803/ (Markdown: https://insights.sbomify.com/CVE-2026-110803/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-110803
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-110803
- OSV: https://osv.dev/vulnerability/CVE-2026-110803

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-110803/
Summaries are generated and may contain mistakes; the official description above is the record.