CVE-2026-77658

/// Technical 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 malicio

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References