{"apiVersion":"1.0","identifier":"CVE-2026-77658","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","publishedAt":"2026-08-26T13:19:22","lastModifiedAt":"2026-08-28T15:44:39","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-77658","cvssScore":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","epssProbability":0.00144,"riskScore":0.79,"affectedProduct":"Dia","affectedVersions":"<=0.98.0","vulnerabilityType":"Library","operatingSystems":[],"links":{"self":"https://www.redsauce.net/api/cves/CVE-2026-77658","webPages":{"es":"https://www.redsauce.net/es/cves/CVE-2026-77658","en":"https://www.redsauce.net/en/cves/CVE-2026-77658","fr":"https://www.redsauce.net/fr/cves/CVE-2026-77658","pt":"https://www.redsauce.net/pt/cves/CVE-2026-77658","de":"https://www.redsauce.net/de/cves/CVE-2026-77658","sk":"https://www.redsauce.net/sk/cves/CVE-2026-77658","el":"https://www.redsauce.net/el/cves/CVE-2026-77658"},"source":"https://nvd.nist.gov/vuln/detail/CVE-2026-77658"}}