In the Linux kernel, the following vulnerability has been resolved:
xfrm: add NULL check in xfrm_update_ae_params
Normally, x->replay_esn and x->preplay_esn should be allocated at
xfrm_alloc_replay_state_esn(...) in xfrm_state_construct(...), hence the
xfrm_update_ae_params(...) is okay to update them. However, the current
implementation of xfrm_new_ae(...) allows a malicious user to directly
dereference a NULL pointer and crash the kernel like below.
BUG: kernel NULL pointer dereference, address: 0000000000000000
PGD 8253067 P4D 8253067 PUD 8e0e067 PMD 0
Oops: 0002 [#1] PREEMPT SMP KASAN NOPTI
CPU: 0 PID: 98 Comm: poc.npd Not tainted 6.4.0-rc7-00072-gdad9774deaf1 #8
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.o4
RIP: 0010:memcpy_orig+0xad/0x140
Code: e8 4c 89 5f e0 48 8d 7f e0 73 d2 83 c2 20 48 29 d6 48 29 d7 83 fa 10 72 34 4c 8b 06 4c 8b 4e 08 c
RSP: 0018:ffff888008f57658 EFLAGS: 00000202
RAX: 0000000000000000 RBX: ffff888008bd0000 RCX: ffffffff8238e571
RDX: 0000000000000018 RSI: ffff888007f64844 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff888008f57818
R13: ffff888007f64aa4 R14: 0000000000000000 R15: 0000000000000000
FS: 00000000014013c0(0000) GS:ffff88806d600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000054d8000 CR4: 00000000000006f0
Call Trace:
? __die+0x1f/0x70
? page_fault_oops+0x1e8/0x500
? __pfx_is_prefetch.constprop.0+0x10/0x10
? __pfx_page_fault_oops+0x10/0x10
? _raw_spin_unlock_irqrestore+0x11/0x40
? fixup_exception+0x36/0x460
? _raw_spin_unlock_irqrestore+0x11/0x40
? exc_page_fault+0x5e/0xc0
? asm_exc_page_fault+0x26/0x30
? xfrm_update_ae_params+0xd1/0x260
? memcpy_orig+0xad/0x140
? __pfx__raw_spin_lock_bh+0x10/0x10
xfrm_update_ae_params+0xe7/0x260
xfrm_new_ae+0x298/0x4e0
? __pfx_xfrm_new_ae+0x10/0x10
? __pfx_xfrm_new_ae+0x10/0x10
xfrm_user_rcv_msg+0x25a/0x410
? __pfx_xfrm_user_rcv_msg+0x10/0x10
? __alloc_skb+0xcf/0x210
? stack_trace_save+0x90/0xd0
? filter_irq_stacks+0x1c/0x70
? __stack_depot_save+0x39/0x4e0
? __kasan_slab_free+0x10a/0x190
? kmem_cache_free+0x9c/0x340
? netlink_recvmsg+0x23c/0x660
? sock_recvmsg+0xeb/0xf0
? __sys_recvfrom+0x13c/0x1f0
? __x64_sys_recvfrom+0x71/0x90
? do_syscall_64+0x3f/0x90
? entry_SYSCALL_64_after_hwframe+0x72/0xdc
? copyout+0x3e/0x50
netlink_rcv_skb+0xd6/0x210
? __pfx_xfrm_user_rcv_msg+0x10/0x10
? __pfx_netlink_rcv_skb+0x10/0x10
? __pfx_sock_has_perm+0x10/0x10
? mutex_lock+0x8d/0xe0
? __pfx_mutex_lock+0x10/0x10
xfrm_netlink_rcv+0x44/0x50
netlink_unicast+0x36f/0x4c0
? __pfx_netlink_unicast+0x10/0x10
? netlink_recvmsg+0x500/0x660
netlink_sendmsg+0x3b7/0x700
This Null-ptr-deref bug is assigned CVE-2023-3772. And this commit
adds additional NULL check in xfrm_update_ae_params to fix the NPD.
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
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-25). 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