In the Linux kernel, the following vulnerability has been resolved:
perf: RISC-V: Remove PERF_HES_STOPPED flag checking in riscv_pmu_start()
Since commit 096b52fd2bb4 ("perf: RISC-V: throttle perf events") the
perf_sample_event_took() function was added to report time spent in
overflow interrupts. If the interrupt takes too long, the perf framework
will lower the sysctl_perf_event_sample_rate and max_samples_per_tick.
When hwc->interrupts is larger than max_samples_per_tick, the
hwc->interrupts will be set to MAX_INTERRUPTS, and events will be
throttled within the __perf_event_account_interrupt() function.
However, the RISC-V PMU driver doesn't call riscv_pmu_stop() to update the
PERF_HES_STOPPED flag after perf_event_overflow() in pmu_sbi_ovf_handler()
function to avoid throttling. When the perf framework unthrottled the event
in the timer interrupt handler, it triggers riscv_pmu_start() function
and causes a WARN_ON_ONCE() warning, as shown below:
------------[ cut here ]------------
WARNING: CPU: 0 PID: 240 at drivers/perf/riscv_pmu.c:184 riscv_pmu_start+0x7c/0x8e
Modules linked in:
CPU: 0 PID: 240 Comm: ls Not tainted 6.4-rc4-g19d0788e9ef2 #1
Hardware name: SiFive (DT)
epc : riscv_pmu_start+0x7c/0x8e
ra : riscv_pmu_start+0x28/0x8e
epc : ffffffff80aef864 ra : ffffffff80aef810 sp : ffff8f80004db6f0
gp : ffffffff81c83750 tp : ffffaf80069f9bc0 t0 : ffff8f80004db6c0
t1 : 0000000000000000 t2 : 000000000000001f s0 : ffff8f80004db720
s1 : ffffaf8008ca1068 a0 : 0000ffffffffffff a1 : 0000000000000000
a2 : 0000000000000001 a3 : 0000000000000870 a4 : 0000000000000000
a5 : 0000000000000000 a6 : 0000000000000840 a7 : 0000000000000030
s2 : 0000000000000000 s3 : ffffaf8005165800 s4 : ffffaf800424da00
s5 : ffffffffffffffff s6 : ffffffff81cc7590 s7 : 0000000000000000
s8 : 0000000000000006 s9 : 0000000000000001 s10: ffffaf807efbc340
s11: ffffaf807efbbf00 t3 : ffffaf8006a16028 t4 : 00000000dbfbb796
t5 : 0000000700000000 t6 : ffffaf8005269870
status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000003
[] riscv_pmu_start+0x7c/0x8e
[] perf_adjust_freq_unthr_context+0x15e/0x174
[] perf_event_task_tick+0x88/0x9c
[] scheduler_tick+0xfe/0x27c
[] update_process_times+0x9a/0xba
[] tick_sched_handle+0x32/0x66
[] tick_sched_timer+0x64/0xb0
[] __hrtimer_run_queues+0x156/0x2f4
[] hrtimer_interrupt+0xe2/0x1fe
[] riscv_timer_interrupt+0x38/0x42
[] handle_percpu_devid_irq+0x90/0x1d2
[] generic_handle_domain_irq+0x28/0x36
After referring other PMU drivers like Arm, Loongarch, Csky, and Mips,
they don't call *_pmu_stop() to update with PERF_HES_STOPPED flag
after perf_event_overflow() function nor do they add PERF_HES_STOPPED
flag checking in *_pmu_start() which don't cause this warning.
Thus, it's recommended to remove this unnecessary check in
riscv_pmu_start() function to prevent this warning.
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