{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-63809", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T07:54:57.013Z", "datePublished": "2026-07-19T12:02:11.905Z", "dateUpdated": "2026-08-17T04:51:15.528Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T04:51:15.528Z" }, "descriptions": [ { "lang": "en", "value": "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 \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 \n\nWith this fix applied on top of the same test setup, rerunning the\nreproducer with fail-nth=1 yields no corresponding Oops reports." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The bug is reached only via a local write() to /proc/sys/* through proc_sys_call_handler() → BPF_CGROUP_RUN_PROG_SYSCTL() → __cgroup_bpf_run_filter_sysctl(); there is no network, adjacent-radio, or physical-device entry point.\nAC:L - An attacker controls all prerequisites: they can mount/join a cgroup, load and attach a cgroup/sysctl BPF program that calls bpf_sysctl_set_new_value(), issue a >PAGE_SIZE sysctl write, and induce kmalloc failure (e.g., memory pressure) so kvzalloc() falls back to vmalloc and the wrong kfree() path is taken.\nPR:L - In a user+network namespace (unshare -Urn), CAP_NET_ADMIN grants write access to /proc/sys/net/* sysctls, and CAP_BPF plus CAP_NET_ADMIN suffice to load/attach BPF_PROG_TYPE_CGROUP_SYSCTL; cgroup management is available with namespace CAP_SYS_ADMIN, without init-namespace root.\nUI:N - Exploitation is fully attacker-driven through syscalls (write, bpf) and requires no victim interaction.\nS:U - Impact is kernel memory corruption and potential privilege escalation within the same kernel/host security boundary, not a cross-boundary escape such as VM or IOMMU bypass.\nC:H - Calling kfree() on a vmalloc-backed kvzalloc() buffer corrupts slab allocator metadata and can be leveraged for arbitrary kernel memory disclosure, not merely a bounded leak.\nI:H - Invalid kfree() of vmalloc memory is a heap corruption primitive that can corrupt slab freelists and be developed into arbitrary kernel writes or code execution.\nA:H - The reproducer triggers an immediate kernel oops/page fault in kfree(), and the underlying allocator corruption can also cause panics, hangs, or repeated crashes." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "kernel/bpf/cgroup.c" ], "versions": [ { "version": "b7925acd82926ebbf94a0f0783a3961f4e558856", "lessThan": "d0a81ed5ff5d0f9c3f63a4f9e5a4642c363ecd3e", "status": "affected", "versionType": "git" }, { "version": "4508943794efdd94171549c0bd52810e2f4ad9fe", "lessThan": "77355ef7a9f6b0d2bdf65be3b37f2c1f365e20d2", "status": "affected", "versionType": "git" }, { "version": "4508943794efdd94171549c0bd52810e2f4ad9fe", "lessThan": "e1d1e203a6000804c5d3b8a4aa4e52303c0c7ab2", "status": "affected", "versionType": "git" }, { "version": "4508943794efdd94171549c0bd52810e2f4ad9fe", "lessThan": "81fc9a13acae99966232f0e055eb2e445263b89a", "status": "affected", "versionType": "git" }, { "version": "4508943794efdd94171549c0bd52810e2f4ad9fe", "lessThan": "838fe9c28121777c59a9406710a68fcf77bb8017", "status": "affected", "versionType": "git" }, { "version": "4508943794efdd94171549c0bd52810e2f4ad9fe", "lessThan": "65bd0c0afb0e1bf3287458e342429b069624f7d4", "status": "affected", "versionType": "git" }, { "version": "4508943794efdd94171549c0bd52810e2f4ad9fe", "lessThan": "70df4de46577fab5e25418f014583155a147c902", "status": "affected", "versionType": "git" }, { "version": "4508943794efdd94171549c0bd52810e2f4ad9fe", "lessThan": "4c21b5927d4364bfe7365f2700da5fea0ed0d004", "status": "affected", "versionType": "git" }, { "version": "66258ab303588936ee1ee0794d9a271be24f73cb", "status": "affected", "versionType": "git" }, { "version": "5.10.20", "lessThan": "5.10.260", "status": "affected", "versionType": "semver" }, { "version": "5.11.3", "lessThan": "5.12", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "kernel/bpf/cgroup.c" ], "versions": [ { "version": "5.12", "status": "affected" }, { "version": "0", "lessThan": "5.12", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.260", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.211", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.177", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.144", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.95", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.38", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.3", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.10.20", "versionEndExcluding": "5.10.260" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12", "versionEndExcluding": "5.15.211" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12", "versionEndExcluding": "6.1.177" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12", "versionEndExcluding": "6.6.144" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12", "versionEndExcluding": "6.12.95" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12", "versionEndExcluding": "6.18.38" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12", "versionEndExcluding": "7.1.3" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12", "versionEndExcluding": "7.2" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/d0a81ed5ff5d0f9c3f63a4f9e5a4642c363ecd3e" }, { "url": "https://git.kernel.org/stable/c/77355ef7a9f6b0d2bdf65be3b37f2c1f365e20d2" }, { "url": "https://git.kernel.org/stable/c/e1d1e203a6000804c5d3b8a4aa4e52303c0c7ab2" }, { "url": "https://git.kernel.org/stable/c/81fc9a13acae99966232f0e055eb2e445263b89a" }, { "url": "https://git.kernel.org/stable/c/838fe9c28121777c59a9406710a68fcf77bb8017" }, { "url": "https://git.kernel.org/stable/c/65bd0c0afb0e1bf3287458e342429b069624f7d4" }, { "url": "https://git.kernel.org/stable/c/70df4de46577fab5e25418f014583155a147c902" }, { "url": "https://git.kernel.org/stable/c/4c21b5927d4364bfe7365f2700da5fea0ed0d004" } ], "title": "bpf: use kvfree() for replaced sysctl write buffer", "x_generator": { "engine": "bippy-1.2.0" } } } }