{"id":"CVE-2026-19820","state":"PUBLISHED","title":"Backblaze Client for Windows Improper Link Resolution Vulnerability","description":"A vulnerability in the Backblaze Client allows a local user to make the system not bootable by creating a link from Backblaze's folder to Windows OS system files during a backup. Successful exploitation requires an administrator-level system change that results in the absence of specific Windows OS security controls. This vulnerability is due to improper link resolution.","publishedAt":"2026-09-01T00:13:03.935Z","updatedAt":"2026-09-10T23:32:25.536Z","severity":{"score":5.8,"label":"Medium","version":"4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:L/SA:L","source":"Bugcrowd"},"assigner":"Bugcrowd","products":["Backblaze Backblaze Client"],"affected":[{"vendor":"Backblaze","product":"Backblaze Client","defaultStatus":"unaffected","versions":[{"version":"10.0.0.1029","status":"affected","versionType":"custom"},{"version":"10.0.1.1037","status":"affected","versionType":"custom"},{"version":"10.0.2.1047","status":"affected","versionType":"custom"}],"platforms":["Windows"]}],"references":["https://www.backblaze.com/computer-backup/docs/backup-client-release-notes-windows","https://www.backblaze.com/status/update"],"weaknesses":["CWE-59"],"ingestedAt":"2026-10-29T20:11:10.572Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/19xxx/CVE-2026-19820.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-19820","state":"PUBLISHED","datePublished":"2026-09-01T00:13:03.935Z","dateUpdated":"2026-09-10T23:32:25.536Z","assignerShortName":"Bugcrowd","assignerOrgId":"4ac701fe-44e9-4bcd-9585-dd6449257611","dateReserved":"2026-08-14T05:28:19.979Z"},"containers":{"cna":{"title":"Backblaze Client for Windows Improper Link Resolution Vulnerability","descriptions":[{"lang":"en","value":"A vulnerability in the Backblaze Client allows a local user to make the system not bootable by creating a link from Backblaze's folder to Windows OS system files during a backup. Successful exploitation requires an administrator-level system change that results in the absence of specific Windows OS security controls. This vulnerability is due to improper link resolution."}],"affected":[{"vendor":"Backblaze","product":"Backblaze Client","defaultStatus":"unaffected","versions":[{"version":"10.0.0.1029","status":"affected","versionType":"custom"},{"version":"10.0.1.1037","status":"affected","versionType":"custom"},{"version":"10.0.2.1047","status":"affected","versionType":"custom"}],"platforms":["Windows"]}],"references":[{"url":"https://www.backblaze.com/computer-backup/docs/backup-client-release-notes-windows"},{"url":"https://www.backblaze.com/status/update"}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV4_0":{"baseScore":5.8,"baseSeverity":"MEDIUM","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:L/SA:L","version":"4.0"}}],"problemTypes":[{"descriptions":[{"lang":"en","description":"CWE-59 Improper Link Resolution Before File Access"}]}],"providerMetadata":{"shortName":"Bugcrowd","orgId":"4ac701fe-44e9-4bcd-9585-dd6449257611","dateUpdated":"2026-09-10T23:32:25.536Z"},"credits":[{"lang":"en","value":"TrendAI Zero Day Initiative","type":"coordinator"},{"lang":"en","value":"hamdi","type":"finder"}]},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-01T15:13:42.323998Z","id":"CVE-2026-19820","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-59","type":"CWE","lang":"en","description":"CWE-59 Improper Link Resolution Before File Access ('Link Following')"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-01T15:14:13.872Z"}}]}}}