{"id":"CVE-2026-90954","state":"PUBLISHED","title":"Busybox: busybox: dpkg-deb extraction-root escape via per-ar-member deferred symlink flush","description":"A flaw was found in BusyBox's dpkg-deb archive extraction. The ar archive handler flushes deferred symlinks after each archive member, unlike the tar, cpio, and unzip handlers which flush once after the last member. A specially crafted .deb archive with two data.tar members can exploit this ordering: the first member declares a symlink pointing to an absolute path (e.g., '/'), which is deferred as unsafe but flushed after the first member. The second member declares a regular file whose path traverses the now-live symlink, resulting in a file being written outside the intended extraction directory. This could allow an attacker to write arbitrary files to arbitrary locations when a user extracts a crafted .deb package.","publishedAt":"2026-10-14T10:00:08.215Z","updatedAt":"2026-10-19T19:04:36.467Z","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":"redhat"},"assigner":"redhat","products":["Red Hat Red Hat Hardened Images"],"affected":[{"vendor":"Red Hat","product":"Red Hat Hardened Images","packageName":"busybox","defaultStatus":"affected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/a:redhat:hummingbird:1"]}],"references":["https://access.redhat.com/security/cve/CVE-2026-90954","https://bugzilla.redhat.com/show_bug.cgi?id=2533007"],"weaknesses":["CWE-59"],"ingestedAt":"2026-10-29T20:13:34.582Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/90xxx/CVE-2026-90954.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-90954","state":"PUBLISHED","datePublished":"2026-10-14T10:00:08.215Z","dateUpdated":"2026-10-19T19:04:36.467Z","assignerShortName":"redhat","assignerOrgId":"53f830b8-0a3f-465b-8143-3b8a9948e749","dateReserved":"2026-09-14T11:58:18.067Z"},"containers":{"cna":{"title":"Busybox: busybox: dpkg-deb extraction-root escape via per-ar-member deferred symlink flush","descriptions":[{"lang":"en","value":"A flaw was found in BusyBox's dpkg-deb archive extraction. The ar archive handler flushes deferred symlinks after each archive member, unlike the tar, cpio, and unzip handlers which flush once after the last member. A specially crafted .deb archive with two data.tar members can exploit this ordering: the first member declares a symlink pointing to an absolute path (e.g., '/'), which is deferred as unsafe but flushed after the first member. The second member declares a regular file whose path traverses the now-live symlink, resulting in a file being written outside the intended extraction directory. This could allow an attacker to write arbitrary files to arbitrary locations when a user extracts a crafted .deb package."}],"affected":[{"vendor":"Red Hat","product":"Red Hat Hardened Images","packageName":"busybox","defaultStatus":"affected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/a:redhat:hummingbird:1"]}],"references":[{"url":"https://access.redhat.com/security/cve/CVE-2026-90954","tags":["vdb-entry","x_refsource_REDHAT"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2533007","name":"RHBZ#2533007","tags":["issue-tracking","x_refsource_REDHAT"]}],"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-59","description":"Improper Link Resolution Before File Access ('Link Following')","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"redhat","orgId":"53f830b8-0a3f-465b-8143-3b8a9948e749","dateUpdated":"2026-10-14T10:00:08.215Z"},"datePublic":"2026-10-14T08:00:00.000Z","x_redhatCweChain":"CWE-59: Improper Link Resolution Before File Access ('Link Following')","workarounds":[{"lang":"en","value":"Do not use BusyBox dpkg-deb to extract untrusted .deb packages. Use Debian's reference dpkg-deb implementation, which treats the extraction root as a boundary and is not affected by this issue. If BusyBox dpkg-deb must be used, inspect .deb archives for multiple data.tar members before extraction (legitimate .deb packages contain exactly one data.tar member)."}],"timeline":[{"lang":"en","time":"2026-09-14T00:00:00.000Z","value":"Reported to Red Hat."},{"lang":"en","time":"2026-10-14T08:00:00.000Z","value":"Made public."}],"credits":[{"lang":"en","value":"Red Hat would like to thank Shubham Raj (Causal Security) for reporting this issue."}],"x_generator":{"engine":"cvelib 1.8.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-19T19:04:23.866850Z","id":"CVE-2026-90954","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T19:04:36.467Z"}}]}}}