CVE-2026-77658 Dia: dia: stack buffer overflow in bus object via unvalidated handle count in project files
Attacker can cause stack buffer overflow and potential code execution by tricking a user into opening a malicious Dia project file with excessive handle counts.
- 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
- None listed
What is CVE-2026-77658?
CVE-2026-77658 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 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
Weakness: CWE-121
Which versions are affected by CVE-2026-77658?
How do I fix CVE-2026-77658?
No fix has been published for CVE-2026-77658 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-77658 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-77658 exists.
Sources
Also known as DEBIAN-CVE-2026-77658, GHSA-ff24-wmrj-75w8, UBUNTU-CVE-2026-77658.