---
cve: "CVE-2026-77658"
severity: "HIGH"
cvss: 7.8
epss: "0.1%"
vendor: "Gnome"
kev: false
exploited: false
published: "2026-08-26 13:19:22"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-22T08:20:44+02:00"
---

# CVE-2026-77658

> 7.8 HIGH

## Beschreibung

A stack-based buffer overflow vulnerability exists in the Dia diagram editor when processing Network Bus objects from Dia XML project files.

In objects/network/bus.c, bus_load() reads the number of bus handles from the file attribute "bus_handles" using attribute_num_data() without validating an upper bound:

    bus->num_handles = attribute_num_data(attr);

When a bus handle is subsequently moved, bus_handle_moved() allocates two temporary arrays on the stack:

    parallel = (real *)g_alloca(num_handles * sizeof(real));
    perp = (real *)g_alloca(num_handles * sizeof(real));

Because num_handles is fully attacker-controlled via the project file, sufficiently large values (for example 262144 or higher) cause g_alloca() to consume more stack space than the default thread stack limit (typically 8 MB on Linux), resulting in stack overflow, SIGSEGV, and potential stack frame / return-address corruption.

An attacker can embed a Bus object with an excessive bus_handles count in a malicious .dia file. Exploitation requires the victim to open the file in Dia (file dialog, command line, or file association) and trigger handle manipulation (moving a bus handle), which exercises the vulnerable code path.

The identical g_alloca pattern is present in objects/Misc/tree.c (copied from bus.c) and is likely vulnerable to the same class of attack via Tree objects.

Affected versions: Dia 0.98.0 and earlier versions containing this code; issue confirmed on upstream master as of 2026-08-21.
Upstream report: https://gitlab.gnome.org/GNOME/dia/-/issues/581

## CVSS-Vektor

```
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Lokal | good |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Erforderlich | good |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Referenzen

- <https://access.redhat.com/security/cve/CVE-2026-77658>
- <https://bugzilla.redhat.com/show_bug.cgi?id=2520890>
- <https://gitlab.gnome.org/GNOME/dia/-/blob/master/objects/network/bus.c>
- <https://gitlab.gnome.org/GNOME/dia/-/issues/581>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-77658) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_