In the Linux kernel, the following vulnerability has been resolved:
ACPI: PPTT: Fix to avoid sleep in the atomic context when PPTT is absent
Commit 0c80f9e165f8 ("ACPI: PPTT: Leave the table mapped for the runtime usage")
enabled to map PPTT once on the first invocation of acpi_get_pptt() and
never unmapped the same allowing it to be used at runtime with out the
hassle of mapping and unmapping the table. This was needed to fetch LLC
information from the PPTT in the cpuhotplug path which is executed in
the atomic context as the acpi_get_table() might sleep waiting for a
mutex.
However it missed to handle the case when there is no PPTT on the system
which results in acpi_get_pptt() being called from all the secondary
CPUs attempting to fetch the LLC information in the atomic context
without knowing the absence of PPTT resulting in the splat like below:
| BUG: sleeping function called from invalid context at kernel/locking/semaphore.c:164
| in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 0, name: swapper/1
| preempt_count: 1, expected: 0
| RCU nest depth: 0, expected: 0
| no locks held by swapper/1/0.
| irq event stamp: 0
| hardirqs last enabled at (0): 0x0
| hardirqs last disabled at (0): copy_process+0x61c/0x1b40
| softirqs last enabled at (0): copy_process+0x61c/0x1b40
| softirqs last disabled at (0): 0x0
| CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.3.0-rc1 #1
| Call trace:
| dump_backtrace+0xac/0x138
| show_stack+0x30/0x48
| dump_stack_lvl+0x60/0xb0
| dump_stack+0x18/0x28
| __might_resched+0x160/0x270
| __might_sleep+0x58/0xb0
| down_timeout+0x34/0x98
| acpi_os_wait_semaphore+0x7c/0xc0
| acpi_ut_acquire_mutex+0x58/0x108
| acpi_get_table+0x40/0xe8
| acpi_get_pptt+0x48/0xa0
| acpi_get_cache_info+0x38/0x140
| init_cache_level+0xf4/0x118
| detect_cache_attributes+0x2e4/0x640
| update_siblings_masks+0x3c/0x330
| store_cpu_topology+0x88/0xf0
| secondary_start_kernel+0xd0/0x168
| __secondary_switched+0xb8/0xc0
Update acpi_get_pptt() to consider the fact that PPTT is once checked and
is not available on the system and return NULL avoiding any attempts to
fetch PPTT and thereby avoiding any possible sleep waiting for a mutex
in the atomic context.
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 2026-10-17). 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 (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.
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