Description
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
Published: n/a
Score: 7.8 High
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Impact

The Dia diagram editor contains a stack‑based buffer overflow that is triggered when a Network Bus object in a .dia project file specifies an excessively large number of bus handles. The unvalidated bus_handles attribute allows an attacker to control the amount of memory allocated on the stack via g_alloca(), potentially exceeding the thread stack limit and overwriting the return address. This overflow could cause the program to crash or, if crafted data is supplied, enable arbitrary code execution.

Affected Systems

The software affected is the Dia diagram editor, versions 0.98.0 and earlier. All users running these releases and who may open untrusted diagram files are at risk.

Risk and Exploitability

The CVSS score of 7.8 indicates a high local impact; no EPSS score is available and the vulnerability is not listed in CISA’s KEV catalog. Exploitation requires a user to open a malicious .dia file, typically via the file dialog or command line, and then manipulate a bus handle to trigger the vulnerable code path. The attack vector is local, but the potential to corrupt memory and possibly execute arbitrary code makes it a significant threat for systems that use Dia.

Generated by OpenCVE AI on August 25, 2026 at 14:10 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Upgrade Dia to the latest release that includes the bus handle validation fix.
  • If an update is not immediately possible, avoid opening or manipulating .dia files from untrusted sources.
  • Where possible, limit the number of bus handles in project files or apply a custom patch that enforces bounds checking on bus_handles.

Generated by OpenCVE AI on August 25, 2026 at 14:10 UTC.

Tracking

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Advisories

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History

Tue, 25 Aug 2026 14:15:00 +0000

Type Values Removed Values Added
First Time appeared Gnome
Gnome dia
Vendors & Products Gnome
Gnome dia

Tue, 25 Aug 2026 12:15:00 +0000

Type Values Removed Values Added
Description 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
Title dia: dia: stack buffer overflow in Bus object via unvalidated handle count in project files
Weaknesses CWE-121
References
Metrics threat_severity

None

 cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H'}

threat_severity

Important

Subscriptions

Gnome Dia
cve-icon MITRE

No data.

cve-icon Vulnrichment

No data.

cve-icon NVD

No data.

cve-icon Redhat

Severity : Important

Publid Date: 2026-08-21T00:00:00Z

Links: CVE-2026-77658 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-08-25T14:15:05Z

Weaknesses
  • CWE-121

    Stack-based Buffer Overflow