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:
? __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
...
With this fix applied on top of the same test setup, rerunning the
reproducer with fail-nth=1 yields no corresponding Oops reports.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.8): severity, escalated by confirmed exploitation. This CVE's 7.8 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.8 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-24). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it