{"document":{"category":"csaf_vex","csaf_version":"2.0","title":"CVE-2026-52906: 9p: fix access mode flags being ORed instead of replaced","publisher":{"category":"vendor","name":"HarborGuard Database","namespace":"https://database.harborguard.co"},"tracking":{"id":"CVE-2026-52906","status":"final","version":"1","initial_release_date":"2026-06-09T12:36:03.521Z","current_release_date":"2026-06-14T04:30:31.711Z","revision_history":[{"date":"2026-06-09T12:36:03.521Z","number":"1","summary":"Initial machine-readable export from HarborGuard."}]},"distribution":{"tlp":{"label":"WHITE"},"text":"Public CVE data; freely redistributable."},"notes":[{"category":"description","text":"In the Linux kernel, the following vulnerability has been resolved:\n\n9p: fix access mode flags being ORed instead of replaced\n\nSince commit 1f3e4142c0eb (\"9p: convert to the new mount API\"),\nv9fs_apply_options() applies parsed mount flags with |= onto flags\nalready set by v9fs_session_init(). For 9P2000.L, session_init sets\nV9FS_ACCESS_CLIENT as the default, so when the user mounts with\n\"access=user\", both bits end up set. Access mode checks compare\nagainst exact values, so having both bits set matches neither mode.\n\nThis causes v9fs_fid_lookup() to fall through to the default switch\ncase, using INVALID_UID (nobody/65534) instead of current_fsuid()\nfor all fid lookups. Root is then unable to chown or perform other\nprivileged operations.\n\nFix by clearing the access mask before applying the user's choice.","title":"CVE description"}],"references":[{"category":"self","summary":"CVE-2026-52906 on HarborGuard Database","url":"https://database.harborguard.co/cve/CVE-2026-52906"},{"category":"external","summary":"CVE Record","url":"https://www.cve.org/CVERecord?id=CVE-2026-52906"},{"category":"external","summary":"git.kernel.org","url":"https://git.kernel.org/stable/c/b8f037e87a083291190204b959cda417aaf01058"},{"category":"external","summary":"git.kernel.org","url":"https://git.kernel.org/stable/c/da2346a48a5a1fed86c3fe3d73c0b60e7b3027c9"}]},"product_tree":{"branches":[{"category":"vendor","name":"Linux","branches":[{"category":"product_name","name":"Linux","branches":[{"category":"product_version_range","name":">=1f3e4142c0eb178089ea0cbc97506a061470ad27 <b8f037e87a083291190204b959cda417aaf01058","product":{"name":"Linux Linux >=1f3e4142c0eb178089ea0cbc97506a061470ad27 <b8f037e87a083291190204b959cda417aaf01058","product_id":"CSAFPID-1","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:*"}}},{"category":"product_version_range","name":">=1f3e4142c0eb178089ea0cbc97506a061470ad27 <da2346a48a5a1fed86c3fe3d73c0b60e7b3027c9","product":{"name":"Linux Linux >=1f3e4142c0eb178089ea0cbc97506a061470ad27 <da2346a48a5a1fed86c3fe3d73c0b60e7b3027c9","product_id":"CSAFPID-2","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:*"}}}]}]},{"category":"vendor","name":"Linux","branches":[{"category":"product_name","name":"Linux","branches":[{"category":"product_version","name":"6.19","product":{"name":"Linux Linux 6.19","product_id":"CSAFPID-3","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:6.19:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"0","product":{"name":"Linux Linux 0","product_id":"CSAFPID-4","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:6.19:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"7.0.4","product":{"name":"Linux Linux 7.0.4","product_id":"CSAFPID-5","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:6.19:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"7.1-rc1","product":{"name":"Linux Linux 7.1-rc1","product_id":"CSAFPID-6","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:6.19:*:*:*:*:*:*:*"}}}]}]}]},"vulnerabilities":[{"cve":"CVE-2026-52906","title":"9p: fix access mode flags being ORed instead of replaced","notes":[{"category":"description","text":"In the Linux kernel, the following vulnerability has been resolved:\n\n9p: fix access mode flags being ORed instead of replaced\n\nSince commit 1f3e4142c0eb (\"9p: convert to the new mount API\"),\nv9fs_apply_options() applies parsed mount flags with |= onto flags\nalready set by v9fs_session_init(). For 9P2000.L, session_init sets\nV9FS_ACCESS_CLIENT as the default, so when the user mounts with\n\"access=user\", both bits end up set. Access mode checks compare\nagainst exact values, so having both bits set matches neither mode.\n\nThis causes v9fs_fid_lookup() to fall through to the default switch\ncase, using INVALID_UID (nobody/65534) instead of current_fsuid()\nfor all fid lookups. Root is then unable to chown or perform other\nprivileged operations.\n\nFix by clearing the access mask before applying the user's choice.","title":"CVE description"}],"product_status":{"known_affected":["CSAFPID-1","CSAFPID-2","CSAFPID-3"],"fixed":["CSAFPID-4","CSAFPID-5","CSAFPID-6"]},"scores":[{"cvss_v3":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","baseScore":7.7,"baseSeverity":"HIGH"},"products":["CSAFPID-1","CSAFPID-2","CSAFPID-3"]}],"remediations":[{"category":"vendor_fix","details":"Update to a fixed version: 0, 7.0.4, 7.1-rc1, b8f037e87a083291190204b959cda417aaf01058, da2346a48a5a1fed86c3fe3d73c0b60e7b3027c9.","product_ids":["CSAFPID-1","CSAFPID-2","CSAFPID-3"]}]}]}