# CVE-2026-77652: Dia: dia: heap buffer overflow in wpg colormap parser via out-of-bounds palette index

> Heap buffer overflow in Dia's WPG parser allows arbitrary code execution or crash when a user opens a malicious WPG file.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 26 Aug 2026
- **Updated:** 27 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-77652, GHSA-w4q3-279c-xvrv, UBUNTU-CVE-2026-77652

## What is CVE-2026-77652?

CVE-2026-77652 is a high-severity memory corruption vulnerability in GNOME Dia, published on 26 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

A heap-based buffer overflow vulnerability exists in the Dia diagram editor WPG file format importer.

In plug-ins/wpg/wpg-import.c, the WPG import renderer allocates a fixed palette with:

    ren->pPal = g_new0(WPGColorRGB, 256);

When handling a WPG_COLORMAP record, the parser reads a start index (i16) and number of colors (iNum16) from the file and reads palette data with:

    bRet &= (iNum16 == (int)fread(&ren->pPal[i16], sizeof(WPGColorRGB), iNum16, f));

The only bounds-related check is `if (i16 >= 0 && i16 <= iSize)`, where iSize is the WPG record size—not the palette capacity. There is no validation that i16 is less than 256 or that i16 + iNum16 does not exceed 256.

A malicious WPG file can supply i16=256 and iNum16=264. That causes fread() to write 792 bytes starting at &pPal[256], while the palette buffer is only 768 bytes (256 entries × 3 bytes). This overflows into adjacent heap metadata and can crash Dia (SIGABRT / malloc corruption errors) or, depending on heap layout and exploit primitives, potentially lead to arbitrary code execution.

Exploitation requires convincing a user to open a crafted WPG file via Dia's file dialog, command line, or file association. No special privileges are required to deliver the file to the victim.

Affected component: WPG parser (plug-ins/wpg/wpg-import.c).
Affected versions: all Dia versions containing this code path (reporter tested Dia 0.98+git20260221-1; issue present on upstream master as of 2026-08-21).

Weakness: CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-77652?


## How do I fix CVE-2026-77652?

No fix has been published for CVE-2026-77652 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-77652 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-77652 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77652 and fix it if it is affected.

What it is: CVE-2026-77652 is a high-severity memory corruption vulnerability in GNOME Dia, published on 26 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-77652 exists.

Affected product: GNOME Dia. 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-2026-77652/ (Markdown: https://insights.sbomify.com/CVE-2026-77652/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77652
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77652
- OSV: https://osv.dev/vulnerability/CVE-2026-77652

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-77652/
Summaries are generated and may contain mistakes; the official description above is the record.