In the Linux kernel, the following vulnerability has been resolved:
io_uring/rsrc: validate buffer count with offset for cloning
syzbot reports that it can trigger a WARN_ON() for kmalloc() attempt
that's too big:
WARNING: CPU: 0 PID: 6488 at mm/slub.c:5024 __kvmalloc_node_noprof+0x520/0x640 mm/slub.c:5024
Modules linked in:
CPU: 0 UID: 0 PID: 6488 Comm: syz-executor312 Not tainted 6.15.0-rc7-syzkaller-gd7fa1af5b33e #0 PREEMPT
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
pstate: 20400005 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __kvmalloc_node_noprof+0x520/0x640 mm/slub.c:5024
lr : __do_kmalloc_node mm/slub.c:-1 [inline]
lr : __kvmalloc_node_noprof+0x3b4/0x640 mm/slub.c:5012
sp : ffff80009cfd7a90
x29: ffff80009cfd7ac0 x28: ffff0000dd52a120 x27: 0000000000412dc0
x26: 0000000000000178 x25: ffff7000139faf70 x24: 0000000000000000
x23: ffff800082f4cea8 x22: 00000000ffffffff x21: 000000010cd004a8
x20: ffff0000d75816c0 x19: ffff0000dd52a000 x18: 00000000ffffffff
x17: ffff800092f39000 x16: ffff80008adbe9e4 x15: 0000000000000005
x14: 1ffff000139faf1c x13: 0000000000000000 x12: 0000000000000000
x11: ffff7000139faf21 x10: 0000000000000003 x9 : ffff80008f27b938
x8 : 0000000000000002 x7 : 0000000000000000 x6 : 0000000000000000
x5 : 00000000ffffffff x4 : 0000000000400dc0 x3 : 0000000200000000
x2 : 000000010cd004a8 x1 : ffff80008b3ebc40 x0 : 0000000000000001
Call trace:
__kvmalloc_node_noprof+0x520/0x640 mm/slub.c:5024 (P)
kvmalloc_array_node_noprof include/linux/slab.h:1065 [inline]
io_rsrc_data_alloc io_uring/rsrc.c:206 [inline]
io_clone_buffers io_uring/rsrc.c:1178 [inline]
io_register_clone_buffers+0x484/0xa14 io_uring/rsrc.c:1287
__io_uring_register io_uring/register.c:815 [inline]
__do_sys_io_uring_register io_uring/register.c:926 [inline]
__se_sys_io_uring_register io_uring/register.c:903 [inline]
__arm64_sys_io_uring_register+0x42c/0xea8 io_uring/register.c:903
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767
el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600
which is due to offset + buffer_count being too large. The registration
code checks only the total count of buffers, but given that the indexing
is an array, it should also check offset + count. That can't exceed
IORING_MAX_REG_BUFFERS either, as there's no way to reach buffers beyond
that limit.
There's no issue with registrering a table this large, outside of the
fact that it's pointless to register buffers that cannot be reached, and
that it can trigger this kmalloc() warning for attempting an allocation
that is too large.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (5.5): severity, escalated by confirmed exploitation. This CVE's 5.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.5 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.1% 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, and whom BOD 26-04 binds: 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 (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from 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.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” 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