{"api_version":"1","generated_at":"2026-07-24T21:17:47+00:00","cve":"CVE-2026-63795","urls":{"html":"https://cve.report/CVE-2026-63795","api":"https://cve.report/api/cve/CVE-2026-63795.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-63795","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-63795"},"summary":{"title":"9p: avoid putting oldfid in p9_client_walk() error path","description":"In the Linux kernel, the following vulnerability has been resolved:\n\n9p: avoid putting oldfid in p9_client_walk() error path\n\nWhen p9_client_walk() is called with clone set to false, fid aliases\noldfid. If the walk subsequently fails after the request has been sent,\nthe error path jumps to clunk_fid, which currently calls p9_fid_put(fid)\nunconditionally.\n\nThis drops a reference to oldfid even though ownership of oldfid remains\nwith the caller. If this is the last reference, oldfid can be clunked and\ndestroyed while the caller still expects it to be valid. A later use or\nput of oldfid can then trigger a use-after-free or refcount underflow.\n\nFix this by only putting fid in the clunk_fid error path when it does not\nalias oldfid, matching the existing guard in the error path below.\n\nThis can be triggered when a multi-component walk is split into multiple\np9_client_walk() calls and a later non-cloning walk fails. A reproducer\nand refcount warning logs are available on request.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-07-19 12:16:51","updated_at":"2026-07-20 15:16:46"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"10","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","baseScore":10,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"CHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"10","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","data":{"baseScore":10,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/a61bdcba4f64c2f90d01461913f429ab151f1ca6","name":"https://git.kernel.org/stable/c/a61bdcba4f64c2f90d01461913f429ab151f1ca6","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/b84f46179c806450b89821221ea5bd9a1698aba8","name":"https://git.kernel.org/stable/c/b84f46179c806450b89821221ea5bd9a1698aba8","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/6dbe9443d9f5f7fb6d319a7b77108853ae6c6bea","name":"https://git.kernel.org/stable/c/6dbe9443d9f5f7fb6d319a7b77108853ae6c6bea","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/1a3860d46e3eb47dbd60339783cdad7904486b9f","name":"https://git.kernel.org/stable/c/1a3860d46e3eb47dbd60339783cdad7904486b9f","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/99c379ca1e221c3d75c7c804ebbf4e5ee37a3070","name":"https://git.kernel.org/stable/c/99c379ca1e221c3d75c7c804ebbf4e5ee37a3070","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/a7656d368265d085ac9bb85ab31b0cdb72ad8c38","name":"https://git.kernel.org/stable/c/a7656d368265d085ac9bb85ab31b0cdb72ad8c38","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-63795","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63795","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b48dbb998d70b7f48c2ec0a15c3cf47136808e4e 99c379ca1e221c3d75c7c804ebbf4e5ee37a3070 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b48dbb998d70b7f48c2ec0a15c3cf47136808e4e b84f46179c806450b89821221ea5bd9a1698aba8 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b48dbb998d70b7f48c2ec0a15c3cf47136808e4e a61bdcba4f64c2f90d01461913f429ab151f1ca6 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b48dbb998d70b7f48c2ec0a15c3cf47136808e4e 6dbe9443d9f5f7fb6d319a7b77108853ae6c6bea git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 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the Linux kernel, the following vulnerability has been resolved:\n\n9p: avoid putting oldfid in p9_client_walk() error path\n\nWhen p9_client_walk() is called with clone set to false, fid aliases\noldfid. If the walk subsequently fails after the request has been sent,\nthe error path jumps to clunk_fid, which currently calls p9_fid_put(fid)\nunconditionally.\n\nThis drops a reference to oldfid even though ownership of oldfid remains\nwith the caller. If this is the last reference, oldfid can be clunked and\ndestroyed while the caller still expects it to be valid. A later use or\nput of oldfid can then trigger a use-after-free or refcount underflow.\n\nFix this by only putting fid in the clunk_fid error path when it does not\nalias oldfid, matching the existing guard in the error path below.\n\nThis can be triggered when a multi-component walk is split into multiple\np9_client_walk() calls and a later non-cloning walk fails. A reproducer\nand refcount warning logs are available on request."}],"metrics":[{"cvssV3_1":{"baseScore":10,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","version":"3.1"}}],"providerMetadata":{"dateUpdated":"2026-07-20T13:40:06.613Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/99c379ca1e221c3d75c7c804ebbf4e5ee37a3070"},{"url":"https://git.kernel.org/stable/c/b84f46179c806450b89821221ea5bd9a1698aba8"},{"url":"https://git.kernel.org/stable/c/a61bdcba4f64c2f90d01461913f429ab151f1ca6"},{"url":"https://git.kernel.org/stable/c/6dbe9443d9f5f7fb6d319a7b77108853ae6c6bea"},{"url":"https://git.kernel.org/stable/c/a7656d368265d085ac9bb85ab31b0cdb72ad8c38"},{"url":"https://git.kernel.org/stable/c/1a3860d46e3eb47dbd60339783cdad7904486b9f"}],"title":"9p: avoid putting oldfid in p9_client_walk() error path","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-63795","datePublished":"2026-07-19T12:02:04.069Z","dateReserved":"2026-07-19T07:54:57.012Z","dateUpdated":"2026-07-20T13:40:06.613Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-07-19 12:16:51","lastModifiedDate":"2026-07-20 15:16:46","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","baseScore":10,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"CHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":6}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"63795","Ordinal":"1","Title":"9p: avoid putting oldfid in p9_client_walk() error path","CVE":"CVE-2026-63795","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"63795","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\n9p: avoid putting oldfid in p9_client_walk() error path\n\nWhen p9_client_walk() is called with clone set to false, fid aliases\noldfid. If the walk subsequently fails after the request has been sent,\nthe error path jumps to clunk_fid, which currently calls p9_fid_put(fid)\nunconditionally.\n\nThis drops a reference to oldfid even though ownership of oldfid remains\nwith the caller. If this is the last reference, oldfid can be clunked and\ndestroyed while the caller still expects it to be valid. A later use or\nput of oldfid can then trigger a use-after-free or refcount underflow.\n\nFix this by only putting fid in the clunk_fid error path when it does not\nalias oldfid, matching the existing guard in the error path below.\n\nThis can be triggered when a multi-component walk is split into multiple\np9_client_walk() calls and a later non-cloning walk fails. A reproducer\nand refcount warning logs are available on request.","Type":"Description","Title":"9p: avoid putting oldfid in p9_client_walk() error path"}]}}}