{"id":"CVE-2026-63795","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-63795","generatedAt":"2026-10-28T03:39:34.277Z","title":"In the Linux kernel, the following vulnerability has been resolved: 9p: avoid putting oldfid in p9_client_walk() error path When p9_client_walk() is called with clone set to false, fid aliases oldfid.","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.","published":"2026-07-19T12:16:52.000Z","lastModified":"2026-10-19T20:19:20.000Z","status":"Modified","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":10,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H"},"cwe":["CWE-416"],"affected":["linux/linux kernel"],"epss":{"score":0.00615,"percentile":0.49258,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.61%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/1a3860d46e3eb47dbd60339783cdad7904486b9f","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/6dbe9443d9f5f7fb6d319a7b77108853ae6c6bea","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/99c379ca1e221c3d75c7c804ebbf4e5ee37a3070","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a61bdcba4f64c2f90d01461913f429ab151f1ca6","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a7656d368265d085ac9bb85ab31b0cdb72ad8c38","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/b84f46179c806450b89821221ea5bd9a1698aba8","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-63795","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}