{"answers":{"affected":"","exploited":"There is no known exploitation of CVE-2026-89638 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2026-89638 is a high-severity vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-89638 and fix it if it is affected.\n\nWhat it is: CVE-2026-89638 is a high-severity vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-89638 in the wild and no public exploit code.\n\nAffected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-89638/ (Markdown: https://insights.sbomify.com/CVE-2026-89638/index.md)","id":"CVE-2026-89638","markdown":"https://insights.sbomify.com/CVE-2026-89638/index.md","name":"CVE-2026-89638","record":{"aliases":["AZL-100353","BELL-CVE-2026-89638","DEBIAN-CVE-2026-89638","GHSA-7hx7-9jhj-445w","UBUNTU-CVE-2026-89638"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["privilege_escalation"],"network_reachable":"adjacent_or_local","non_default_config":true,"product_category":"Linux kernel SMB client","requires_auth":"low_privilege","summary":"Attackers can retain setuid/setgid bits on SMB files when using specific mount options, leading to privilege escalation upon execution.","user_interaction":"not_required","vuln_class":"privilege_escalation"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[],"cvss":{"score":7.8,"severity":"high","source":"cna","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"cwes":[],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: clear setuid/setgid bit on write with cifsacl/modefromsid/posix extensions\n\nWhen a file has the setuid or setgid bit set and is written to, the VFS\nstrips those bits and issues a setattr with ATTR_KILL_SUID/ATTR_KILL_SGID\ntogether with an ATTR_MODE carrying the already-cleared mode.\n\nBoth cifs_setattr_unix() and cifs_setattr_nounix() unconditionally dropped\nATTR_MODE in that case:\n\n\t/* skip mode change if it's just for clearing setuid/setgid */\n\tif (attrs-\u003eia_valid \u0026 (ATTR_KILL_SUID|ATTR_KILL_SGID))\n\t\tattrs-\u003eia_valid \u0026= ~ATTR_MODE;\n\nThis is fine for the default mount, where the mode is only emulated via\nthe DOS read-only attribute and cannot represent the setuid/setgid bits\nanyway.  However, with the \"cifsacl\" or \"modefromsid\" mount options the\nmode is stored on the server through an ACL (id_mode_to_cifs_acl()), with\nthe SMB3.1.1 POSIX extensions the mode is sent to the server directly,\nand with the SMB1 Unix extensions (cifs_setattr_unix) the mode is sent\nvia CIFSSMBUnixSetPathInfo().  In all those cases dropping ATTR_MODE means\nthe cleared mode is never pushed to the server, so the setuid/setgid bit\nsurvives the write.\n\nThis is a security issue: on local filesystems the setuid bit is stripped\nwhen a file is written, but over these cifs.ko mounts the bit persists on\nthe server, potentially allowing an unexpected privilege escalation on\nsubsequent execution.\n\nFix this in two places:\n\n  1. cifs_setattr_nounix(): only take the \"skip mode change\" shortcut\n     when the mode is emulated via the DOS read-only attribute (i.e.\n     neither cifsacl/modefromsid nor the SMB3.1.1 POSIX extensions are\n     in effect), so that the cleared mode is propagated to the server\n     in the ACL / POSIX cases.\n\n  2. cifs_setattr_unix(): this function is only called when Unix\n     extensions are in effect, so the mode is always stored on the\n     server.  Remove the shortcut entirely so that the cleared mode is\n     always pushed.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"smb: client: clear setuid/setgid bit on write with cifsacl/modefromsid/posix extensions","id":"CVE-2026-89638","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":"privilege_escalation","year":"2026"},"n_packages":0,"n_references":5,"next":{"headline":"cifs: use cifs_invalidate_cache() in cifs_do_truncate() for O_TRUNC","id":"CVE-2026-89639"},"packages":[],"prev":{"headline":"smb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T2","id":"CVE-2026-89637"},"products":["Linux"],"published":"2026-09-11","related":[],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"no","exploitation":"none","technical_impact":"total"},"state":"PUBLISHED","updated":"2026-10-21","vendors":["Linux"]},"summary":"Attackers can retain setuid/setgid bits on SMB files when using specific mount options, leading to privilege escalation upon execution.","url":"https://insights.sbomify.com/CVE-2026-89638/"}