# CVE-2026-107611: Out-of-bounds read in TightVNC Viewer ZRLE palette decoding

> A malicious VNC server can trigger an out-of-bounds read in TightVNC Viewer, leaking heap memory or crashing the application.

- **Severity:** High 7.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 8 Oct 2026
- **Updated:** 8 Oct 2026
- **Also known as:** GHSA-r575-8hw6-vfq3

## What is CVE-2026-107611?

CVE-2026-107611 is a high-severity vulnerability in GlavSoft TightVNC, published on 8 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

An out-of-bounds read vulnerability in the ZRLE decoder of GlavSoft TightVNC Viewer for Windows before 2.8.88 allows a malicious or compromised VNC server to read heap memory beyond the palette allocation and crash the viewer by sending ZRLE-encoded tiles whose palette indices exceed the declared palette size. readPaletteRleTile() and readPackedPaletteTile() use the attacker-supplied index to look up colours without validating it against the palette size; out-of-bounds heap data is copied into the framebuffer (garbled display) or the read faults, terminating the viewer.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-107611?


## How do I fix CVE-2026-107611?

No fix has been published for CVE-2026-107611 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-107611 being exploited?

There is no known exploitation of CVE-2026-107611 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-107611 and fix it if it is affected.

What it is: CVE-2026-107611 is a high-severity vulnerability in GlavSoft TightVNC, published on 8 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-107611 in the wild and no public exploit code.

Affected product: GlavSoft TightVNC. 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-2026-107611/ (Markdown: https://insights.sbomify.com/CVE-2026-107611/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-107611
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-107611
- OSV: https://osv.dev/vulnerability/CVE-2026-107611

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-107611/
Summaries are generated and may contain mistakes; the official description above is the record.