In the Linux kernel, the following vulnerability has been resolved:
i2c: jz4780: Cache host clock rate at probe to prevent CCF prepare_lock deadlock
Fix a severe AB/BA deadlock between the Common Clock Framework (CCF)
and the I2C adapter lock, which triggers when an I2C-controlled clock
generator client (like the Si5351) is registered or modified under the CCF.
During an i2c client clock (generator) frequency change, the CCF acquires its global
'prepare_lock' mutex and the driver calls i2c_transfer() to update the client's
chip registers, stalling for the adapter's I2C bus lock.
Concurrently, an independent, parallel transfer on the same bus (e.g., a GPIO
expander handling LEDs) can hold the I2C adapter lock. Inside this parallel
transfer path, jz4780_i2c_set_speed() calls clk_get_rate() on the host
controller's input clock to calculate bus timings. This call attempts to acquire
the blocked CCF 'prepare_lock', creating a circular dependency that freezes
the system.
The jz4780 host controller clock itself is static and never changes at runtime.
However, calling clk_get_rate() inside the active transfer path introduces
an unnecessary dependency on the CCF internal locks.
Eliminate this synchronous clk_get_rate() call from the active transfer
path by caching the static host peripheral clock rate once - inside the private
jz4780_i2c structure during jz4780_i2c_probe(). Update jz4780_i2c_set_speed()
to use this cached value, safely decoupling active I2C transactions from the
CCF internal locks without any risk of stale timings.
Assisted-by web based Google AI (pinpointing the bug and writing the message).
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
- EG Severity
- Not assessed: no CVSS publishedA missing CVSS is not a severity of zero.
- 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
- No SSVC decision: EchelonGraph has not assessed this CVECISA 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 BOD 26-04 block below.
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