Answer in brief
CVE-2026-63809 records a High severity (CVSS 7.8) vulnerability in bpf: use kvfree() for replaced sysctl write buffer. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=b7925acd82926ebbf94a0f0783a3961f4e558856 <d0a81ed5ff5d0f9c3f63a4f9e5a4642c363ecd3e || >=4508943794efdd94171549c0bd52810e2f4ad9fe <77355ef7a9f6b0d2bdf65be3b37f2c1f365e20d2 || >=4508943794efdd94171549c0bd52810e2f4ad9fe <e1d1e203a6000804c5d3b8a4aa4e52303c0c7ab2 || >=4508943794efdd94171549c0bd52810e2f4ad9fe <81fc9a13acae99966232f0e055eb2e445263b89a || >=4508943794efdd94171549c0bd52810e2f4ad9fe <838fe9c28121777c59a9406710a68fcf77bb8017 || >=4508943794efdd94171549c0bd52810e2f4ad9fe <65bd0c0afb0e1bf3287458e342429b069624f7d4 || >=4508943794efdd94171549c0bd52810e2f4ad9fe <70df4de46577fab5e25418f014583155a147c902 || >=4508943794efdd94171549c0bd52810e2f4ad9fe <4c21b5927d4364bfe7365f2700da5fea0ed0d004 || 66258ab303588936ee1ee0794d9a271be24f73cb || >=5.10.20 <5.10.260 || >=5.11.3 <5.12 | d0a81ed5ff5d0f9c3f63a4f9e5a4642c363ecd3e, 77355ef7a9f6b0d2bdf65be3b37f2c1f365e20d2, e1d1e203a6000804c5d3b8a4aa4e52303c0c7ab2, 81fc9a13acae99966232f0e055eb2e445263b89a, 838fe9c28121777c59a9406710a68fcf77bb8017, 65bd0c0afb0e1bf3287458e342429b069624f7d4, 70df4de46577fab5e25418f014583155a147c902, 4c21b5927d4364bfe7365f2700da5fea0ed0d004, 5.10.260, 5.12 |
| Linux/Linuxgeneric | 5.12 | Not reported |
Published upstream
Jul 19, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 17, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
In the Linux kernel, the following vulnerability has been resolved: bpf: use kvfree() for replaced sysctl write buffer proc_sys_call_handler() allocates its temporary sysctl buffer with kvzalloc() and passes it to __cgroup_bpf_run_filter_sysctl(). Since kvzalloc() may fall back to vmalloc() for large allocations, freeing that buffer with kfree() is wrong and can corrupt memory. Use kvfree() to safely handle both kmalloc and kvzalloc()/vmalloc allocations. The bug was first flagged by an experimental analysis tool we are developing for kernel memory-management bugs while analyzing v6.13-rc1. The tool is still under development and is not yet publicly available. Manual inspection confirms that the bug is still present in v7.1-rc5. Reproduced the bug based on v7.1-rc4 in a QEMU x86_64 guest booted with KASAN and CONFIG_FAILSLAB enabled. To exercise the replacement path, the test tree also included the accompanying fix for the stale ret == 1 check in __cgroup_bpf_run_filter_sysctl(). The reproducer confines failslab injections to the proc_sys_call_handler() range, uses stacktrace-depth=32, and injects fail-nth=1 while writing 8191 bytes to /proc/sys/kernel/domainname from a task in the target cgroup. Under that setup, fail-nth=1 triggered the fault: BUG: unable to handle page fault for address: ffffeb0200024d48 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 SMP KASAN NOPTI CPU: 2 UID: 0 PID: 209 Comm: repro_proc_sys_ Not tainted 7.1.0-rc4-00686-g97625979a5d4 PREEMPT(lazy) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014 RIP: 0010:kfree+0x6e/0x510 ... Call Trace: <TASK> ? __cgroup_bpf_run_filter_sysctl+0x626/0xc30 __cgroup_bpf_run_filter_sysctl+0x74d/0xc30 ? __pfx___cgroup_bpf_run_filter_sysctl+0x10/0x10 ? srso_return_thunk+0x5/0x5f ? __kvmalloc_node_noprof+0x345/0x870 ? proc_sys_call_handler+0x250/0x480 ? srso_return_thunk+0x5/0x5f proc_sys_call_handler+0x3a2/0x480 ? __pfx_proc_sys_call_handler+0x10/0x10 ? srso_return_thunk+0x5/0x5f ? selinux_file_permission+0x39f/0x500 ? srso_return_thunk+0x5/0x5f ? lock_is_held_type+0x9e/0x120 vfs_write+0x98e/0x1000 ... </TASK> With this fix applied on top of the same test setup, rerunning the reproducer with fail-nth=1 yields no corresponding Oops reports.
Quoted source text, attributed separately from HOL analysis.