{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-64136", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2026-64136" ], "published": "2026-07-19T15:41:06Z", "summary": "smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()\n\nCommit 96c4af418586 (\"cifs: Fix locking usage for tcon fields\")\nrefactored cifs code to change cifs_tcp_ses_lock for tc_lock around\ntc_count changes.\n\nThere was missing lock around tc_count increment inside\nsmb2_find_smb_sess_tcon_unlocked().", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.12.75-1+rpt1~bookworm", "1:6.12.87-1+rpt1~bookworm" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.12.75+rpt-rpi-2712", "binary_version": "1:6.12.75-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.75+rpt-rpi-v6", "binary_version": "1:6.12.75-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.75+rpt-rpi-v7", "binary_version": "1:6.12.75-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.75+rpt-rpi-v7l", "binary_version": "1:6.12.75-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.75+rpt-rpi-v8", "binary_version": "1:6.12.75-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.75+rpt-rpi-v8-rt", "binary_version": "1:6.12.75-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-2712", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v6", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v7", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v7l", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v8", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v8-rt", "binary_version": "1:6.12.87-1+rpt1~bookworm" } ] }, "database_specific": { "per_version": { "1:6.12.75-1+rpt1~bookworm": { "linux_commit": "89050b1059997d38d55462b323b099a6436dc10d", "upstream_version": "6.12.75", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.12.92" }, "1:6.12.87-1+rpt1~bookworm": { "linux_commit": "ae4d75fb36deba0fe1a986d9bfae65755e082dd0", "upstream_version": "6.12.87", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.12.92" } } } }, { "package": { "ecosystem": "Raspberry Pi OS:13", "name": "linux" }, "versions": [ "1:6.12.75-1+rpt1", "1:6.18.29-1+rpt1", "1:6.18.33-1+rpt1" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.12.75+rpt-rpi-2712", "binary_version": "1:6.12.75-1+rpt1" }, { "binary_name": "linux-image-6.12.75+rpt-rpi-v6", "binary_version": "1:6.12.75-1+rpt1" }, { "binary_name": "linux-image-6.12.75+rpt-rpi-v7", "binary_version": "1:6.12.75-1+rpt1" }, { "binary_name": "linux-image-6.12.75+rpt-rpi-v8", "binary_version": "1:6.12.75-1+rpt1" }, { "binary_name": "linux-image-6.12.75+rpt-rpi-v8-rt", "binary_version": "1:6.12.75-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-2712", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v6", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v7", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v8", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v8-rt", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-2712", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v6", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v7", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v8", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v8-rt", "binary_version": "1:6.18.33-1+rpt1" } ] }, "database_specific": { "per_version": { "1:6.12.75-1+rpt1": { "linux_commit": "89050b1059997d38d55462b323b099a6436dc10d", "upstream_version": "6.12.75", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.12.92" }, "1:6.18.29-1+rpt1": { "linux_commit": "66318c5b5cd8145a662303af12ed39ac07eb27cc", "upstream_version": "6.18.29", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.34" }, "1:6.18.33-1+rpt1": { "linux_commit": "95b85bebbedcaedfa7ca79116ed38b7376fba412", "upstream_version": "6.18.33", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.34" } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-64136" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/7df1df6f40c0720d30206aa35c0343b962350e0d" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/13fb413ae22a37c69341918a6d651d19a9b0b9b7" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/bf4ebdb19ff9b3cdf992b50715fe61633327416a" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/e374f4e496fef8168784f93a4477d67be34485fd" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/4d8690dace005a38e6dbde9ecce2da3ad85c7c41" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T13:16:28Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 9.8, "cvss_v3_severity": "Critical", "scenario": "AV:N - The flaw is in the in-kernel SMB/CIFS client (fs/smb/client/), reached when processing SMB2 responses received over TCP from a remote server in cifs_demultiplex_thread(). A network-positioned attacker controlling or impersonating the SMB server can drive the vulnerable cancelled-mid handling path.\nAC:L - The attacker controls SMB response timing and can trigger concurrent cifs_put_tcon() via server-initiated disconnect/reconnect, racing the unprotected tc_count increment. Cancelled-mid conditions arise from normal concurrent I/O, signals, and unmount/reconnect activity that the attacker can reliably provoke.\nPR:N - Exploitation requires no local privileges on the victim; a remote malicious or compromised SMB server can attack any client that has an active CIFS mount/session, without the attacker holding an account or capabilities on the victim host.\nUI:N - No victim interaction is needed at exploit time in common deployments where CIFS shares are automounted at boot or persistently connected (cloud file shares, enterprise NAS); the attacker abuses an already-established SMB session rather than requiring a new mount action.\nS:U - Impact is kernel memory corruption and potential local privilege escalation within the same kernel security domain, not a cross-boundary escape such as guest-to-host VM breakout.\nC:H - The race can cause a use-after-free of struct cifs_tcon; UAF of kernel heap objects enables arbitrary memory disclosure through controlled reuse of the freed structure.\nI:H - The UAF leads to subsequent kernel operations (SMB2_close, workqueue handlers) on freed memory, providing a path to arbitrary kernel write and potential code execution via heap grooming.\nA:H - Winning the refcount race causes use-after-free of cifs_tcon with continued kernel use of the freed object, which can trigger kernel oops/panic and denial of service even before full exploitation." } } }