{ "affected": [ { "ranges": [ { "events": [ { "introduced": "b7925acd82926ebbf94a0f0783a3961f4e558856" }, { "fixed": "d0a81ed5ff5d0f9c3f63a4f9e5a4642c363ecd3e" } ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "type": "GIT" }, { "events": [ { "introduced": "4508943794efdd94171549c0bd52810e2f4ad9fe" }, { "fixed": "77355ef7a9f6b0d2bdf65be3b37f2c1f365e20d2" }, { "fixed": "e1d1e203a6000804c5d3b8a4aa4e52303c0c7ab2" }, { "fixed": "81fc9a13acae99966232f0e055eb2e445263b89a" }, { "fixed": "838fe9c28121777c59a9406710a68fcf77bb8017" }, { "fixed": "65bd0c0afb0e1bf3287458e342429b069624f7d4" }, { "fixed": "70df4de46577fab5e25418f014583155a147c902" }, { "fixed": "4c21b5927d4364bfe7365f2700da5fea0ed0d004" } ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "type": "GIT" }, { "events": [ { "introduced": "0" }, { "last_affected": "66258ab303588936ee1ee0794d9a271be24f73cb" } ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "type": "GIT" }, { "events": [ { "introduced": "5.10.20" }, { "fixed": "5.10.260" } ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "type": "GIT" }, { "events": [ { "introduced": "5.11.3" }, { "fixed": "5.12" } ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "type": "GIT" } ] }, { "package": { "ecosystem": "Linux", "name": "Kernel" }, "ranges": [ { "events": [ { "introduced": "0" }, { "fixed": "5.10.260" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "5.11.0" }, { "fixed": "5.15.211" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "5.12.0" }, { "fixed": "6.1.177" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "5.16.0" }, { "fixed": "6.6.144" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "6.2.0" }, { "fixed": "6.12.95" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "6.7.0" }, { "fixed": "6.18.38" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "6.13.0" }, { "fixed": "7.1.3" } ], "type": "ECOSYSTEM" } ] } ], "database_specific": { "cna_assigner": "Linux", "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63809.json" }, "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: use kvfree() for replaced sysctl write buffer\n\nproc_sys_call_handler() allocates its temporary sysctl buffer with\nkvzalloc() and passes it to __cgroup_bpf_run_filter_sysctl(). Since\nkvzalloc() may fall back to vmalloc() for large allocations, freeing\nthat buffer with kfree() is wrong and can corrupt memory.\n\nUse kvfree() to safely handle both kmalloc and kvzalloc()/vmalloc\nallocations.\n\nThe bug was first flagged by an experimental analysis tool we are\ndeveloping for kernel memory-management bugs while analyzing\nv6.13-rc1. The tool is still under development and is not yet publicly\navailable. Manual inspection confirms that the bug is still\npresent in v7.1-rc5.\n\nReproduced the bug based on v7.1-rc4 in a QEMU x86_64 guest booted with\nKASAN and CONFIG_FAILSLAB enabled. To exercise the replacement path, the\ntest tree also included the accompanying fix for the stale ret == 1\ncheck in __cgroup_bpf_run_filter_sysctl(). The reproducer confines\nfailslab injections to the proc_sys_call_handler() range, uses\nstacktrace-depth=32, and injects fail-nth=1 while writing 8191 bytes to\n/proc/sys/kernel/domainname from a task in the target cgroup. Under\nthat setup, fail-nth=1 triggered the fault:\n\n BUG: unable to handle page fault for address: ffffeb0200024d48\n #PF: supervisor read access in kernel mode\n #PF: error_code(0x0000) - not-present page\n PGD 0 P4D 0\n Oops: Oops: 0000 SMP KASAN NOPTI\n CPU: 2 UID: 0 PID: 209 Comm: repro_proc_sys_ Not tainted 7.1.0-rc4-00686-g97625979a5d4 PREEMPT(lazy)\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014\n RIP: 0010:kfree+0x6e/0x510\n ...\n Call Trace:\n \u003cTASK\u003e\n ? __cgroup_bpf_run_filter_sysctl+0x626/0xc30\n __cgroup_bpf_run_filter_sysctl+0x74d/0xc30\n ? __pfx___cgroup_bpf_run_filter_sysctl+0x10/0x10\n ? srso_return_thunk+0x5/0x5f\n ? __kvmalloc_node_noprof+0x345/0x870\n ? proc_sys_call_handler+0x250/0x480\n ? srso_return_thunk+0x5/0x5f\n proc_sys_call_handler+0x3a2/0x480\n ? __pfx_proc_sys_call_handler+0x10/0x10\n ? srso_return_thunk+0x5/0x5f\n ? selinux_file_permission+0x39f/0x500\n ? srso_return_thunk+0x5/0x5f\n ? lock_is_held_type+0x9e/0x120\n vfs_write+0x98e/0x1000\n ...\n \u003c/TASK\u003e\n\nWith this fix applied on top of the same test setup, rerunning the\nreproducer with fail-nth=1 yields no corresponding Oops reports.", "id": "CVE-2026-63809", "modified": "2026-07-21T03:41:54.108810085Z", "published": "2026-07-19T12:02:11.905Z", "references": [ { "type": "WEB", "url": "https://git.kernel.org/stable/c/4c21b5927d4364bfe7365f2700da5fea0ed0d004" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/65bd0c0afb0e1bf3287458e342429b069624f7d4" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/70df4de46577fab5e25418f014583155a147c902" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/77355ef7a9f6b0d2bdf65be3b37f2c1f365e20d2" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/81fc9a13acae99966232f0e055eb2e445263b89a" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/838fe9c28121777c59a9406710a68fcf77bb8017" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/d0a81ed5ff5d0f9c3f63a4f9e5a4642c363ecd3e" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/e1d1e203a6000804c5d3b8a4aa4e52303c0c7ab2" }, { "type": "ADVISORY", "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63809.json" }, { "type": "ADVISORY", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63809" }, { "type": "PACKAGE", "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git" } ], "schema_version": "1.8.0", "severity": [ { "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "type": "CVSS_V3" } ], "summary": "bpf: use kvfree() for replaced sysctl write buffer" }