bpf: use kvfree() for replaced sysctl write buffer
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_
CVE-2026-63809
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-63809
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "b7925acd82926ebbf94a0f0783a3961f4e558856",
"lessThan": "d0a81ed5ff5d0f9c3f63a4f9e5a4642c363ecd3e",
"versionType": "git"
},
{
"status": "affected",
"version": "4508943794efdd94171549c0bd52810e2f4ad9fe",
"lessThan": "77355ef7a9f6b0d2bdf65be3b37f2c1f365e20d2",
"versionType": "git"
},
{
"status": "affected",
"version": "4508943794efdd94171549c0bd52810e2f4ad9fe",
"lessThan": "e1d1e203a6000804c5d3b8a4aa4e52303c0c7ab2",
"versionType": "git"
},
{
"status": "affected",
"version": "4508943794efdd94171549c0bd52810e2f4ad9fe",
"lessThan": "81fc9a13acae99966232f0e055eb2e445263b89a",
"versionType": "git"
},
{
"status": "affected",
"version": "4508943794efdd94171549c0bd52810e2f4ad9fe",
"lessThan": "838fe9c28121777c59a9406710a68fcf77bb8017",
"versionType": "git"
},
{
"status": "affected",
"version": "4508943794efdd94171549c0bd52810e2f4ad9fe",
"lessThan": "65bd0c0afb0e1bf3287458e342429b069624f7d4",
"versionType": "git"
},
{
"status": "affected",
"version": "4508943794efdd94171549c0bd52810e2f4ad9fe",
"lessThan": "70df4de46577fab5e25418f014583155a147c902",
"versionType": "git"
},
{
"status": "affected",
"version": "4508943794efdd94171549c0bd52810e2f4ad9fe",
"lessThan": "4c21b5927d4364bfe7365f2700da5fea0ed0d004",
"versionType": "git"
},
{
"status": "affected",
"version": "66258ab303588936ee1ee0794d9a271be24f73cb",
"versionType": "git"
},
{
"status": "affected",
"version": "5.10.20",
"lessThan": "5.10.260",
"versionType": "semver"
},
{
"status": "affected",
"version": "5.11.3",
"lessThan": "5.12",
"versionType": "semver"
}
],
"programFiles": [
"kernel/bpf/cgroup.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "5.12"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "5.12",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.260",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.211",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.177",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.144",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.95",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.38",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.3",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"kernel/bpf/cgroup.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-63809
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #40837 · Revision 1
- Added to Heist Feed
- Publisher date