In the Linux kernel, the following vulnerability has been resolved:
netfs: Call invalidate_cache only if implemented
Many filesystems such as NFS and Ceph do not implement the
invalidate_cache method. On those filesystems, if writing to the
cache (NETFS_WRITE_TO_CACHE) fails for some reason, the kernel
crashes like this:
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 0 P4D 0
Oops: Oops: 0010 [#1] SMP PTI
CPU: 9 UID: 0 PID: 3380 Comm: kworker/u193:11 Not tainted 6.13.3-cm4all1-hp #437
Hardware name: HP ProLiant DL380 Gen9/ProLiant DL380 Gen9, BIOS P89 10/17/2018
Workqueue: events_unbound netfs_write_collection_worker
RIP: 0010:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 0018:ffff9b86e2ca7dc0 EFLAGS: 00010202
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 7fffffffffffffff
RDX: 0000000000000001 RSI: ffff89259d576a18 RDI: ffff89259d576900
RBP: ffff89259d5769b0 R08: ffff9b86e2ca7d28 R09: 0000000000000002
R10: ffff89258ceaca80 R11: 0000000000000001 R12: 0000000000000020
R13: ffff893d158b9338 R14: ffff89259d576900 R15: ffff89259d5769b0
FS: 0000000000000000(0000) GS:ffff893c9fa40000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000054442e003 CR4: 00000000001706f0
Call Trace:
? __die+0x1f/0x60
? page_fault_oops+0x15c/0x460
? try_to_wake_up+0x2d2/0x530
? exc_page_fault+0x5e/0x100
? asm_exc_page_fault+0x22/0x30
netfs_write_collection_worker+0xe9f/0x12b0
? xs_poll_check_readable+0x3f/0x80
? xs_stream_data_receive_workfn+0x8d/0x110
process_one_work+0x134/0x2d0
worker_thread+0x299/0x3a0
? __pfx_worker_thread+0x10/0x10
kthread+0xba/0xe0
? __pfx_kthread+0x10/0x10
ret_from_fork+0x30/0x50
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1a/0x30
Modules linked in:
CR2: 0000000000000000
This patch adds the missing NULL check.
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. 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 every mission impact level.CISA BOD 26-04: 60 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 every mission impact level.
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (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)60 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 Vulnrichment) · Technical impact partial (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