{"id":"CVE-2026-77658","state":"PUBLISHED","title":"Dia: dia: stack buffer overflow in bus object via unvalidated handle count in project files","description":"A stack-based buffer overflow vulnerability exists in the Dia diagram editor when processing Network Bus objects from Dia XML project files.\n\nIn 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:\n\n    bus->num_handles = attribute_num_data(attr);\n\nWhen a bus handle is subsequently moved, bus_handle_moved() allocates two temporary arrays on the stack:\n\n    parallel = (real *)g_alloca(num_handles * sizeof(real));\n    perp = (real *)g_alloca(num_handles * sizeof(real));\n\nBecause 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.\n\nAn 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.\n\nThe 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.\n\nAffected versions: Dia 0.98.0 and earlier versions containing this code; issue confirmed on upstream master as of 2026-08-21.\nUpstream report: https://gitlab.gnome.org/GNOME/dia/-/issues/581","publishedAt":"2026-08-26T12:10:07.556Z","updatedAt":"2026-08-26T13:11:12.732Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","source":"fedora"},"assigner":"fedora","products":["GNOME Dia"],"affected":[{"vendor":"GNOME","product":"Dia","packageName":"dia","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThanOrEqual":"0.98.0","versionType":"semver"}],"collectionURL":"https://gitlab.gnome.org/GNOME/dia/-/issues/581"}],"references":["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"],"weaknesses":["CWE-121"],"ingestedAt":"2026-10-29T20:13:07.220Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/77xxx/CVE-2026-77658.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-77658","state":"PUBLISHED","datePublished":"2026-08-26T12:10:07.556Z","dateUpdated":"2026-08-26T13:11:12.732Z","assignerShortName":"fedora","assignerOrgId":"92fb86c3-55a5-4fb5-9c3f-4757b9e96dc5","dateReserved":"2026-08-21T04:33:45.481Z"},"containers":{"cna":{"title":"Dia: dia: stack buffer overflow in bus object via unvalidated handle count in project files","descriptions":[{"lang":"en","value":"A stack-based buffer overflow vulnerability exists in the Dia diagram editor when processing Network Bus objects from Dia XML project files.\n\nIn 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:\n\n    bus->num_handles = attribute_num_data(attr);\n\nWhen a bus handle is subsequently moved, bus_handle_moved() allocates two temporary arrays on the stack:\n\n    parallel = (real *)g_alloca(num_handles * sizeof(real));\n    perp = (real *)g_alloca(num_handles * sizeof(real));\n\nBecause 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.\n\nAn 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.\n\nThe 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.\n\nAffected versions: Dia 0.98.0 and earlier versions containing this code; issue confirmed on upstream master as of 2026-08-21.\nUpstream report: https://gitlab.gnome.org/GNOME/dia/-/issues/581"}],"affected":[{"vendor":"GNOME","product":"Dia","packageName":"dia","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThanOrEqual":"0.98.0","versionType":"semver"}],"collectionURL":"https://gitlab.gnome.org/GNOME/dia/-/issues/581"}],"references":[{"url":"https://access.redhat.com/security/cve/CVE-2026-77658","tags":["vdb-entry","x_refsource_REDHAT"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2520890","name":"RHBZ#2520890","tags":["issue-tracking","x_refsource_REDHAT"]},{"url":"https://gitlab.gnome.org/GNOME/dia/-/blob/master/objects/network/bus.c"},{"url":"https://gitlab.gnome.org/GNOME/dia/-/issues/581"}],"metrics":[{"other":{"content":{"value":"Important","namespace":"https://access.redhat.com/security/updates/classification/"},"type":"Red Hat severity rating"}},{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"HIGH","baseScore":7.8,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","version":"3.1"},"format":"CVSS"}],"problemTypes":[{"descriptions":[{"cweId":"CWE-121","description":"Stack-based Buffer Overflow","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"fedora","orgId":"92fb86c3-55a5-4fb5-9c3f-4757b9e96dc5","dateUpdated":"2026-08-26T12:35:08.070Z"},"datePublic":"2026-08-21T00:00:00.000Z","x_redhatCweChain":"CWE-121: Stack-based Buffer Overflow","timeline":[{"lang":"en","time":"2026-08-21T04:16:10.319Z","value":"Reported to Red Hat."},{"lang":"en","time":"2026-08-21T00:00:00.000Z","value":"Made public."}],"credits":[{"lang":"en","value":"Red Hat would like to thank Robin \"drzobin\" Larsson for reporting this issue."}],"x_generator":{"engine":"cvelib 1.8.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-26T13:09:44.563034Z","id":"CVE-2026-77658","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-26T13:11:12.732Z"}}]}}}