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CVE.org (no NVD analysis yet)· CNA zephyr

CVE-2026-90585: Renesas RA SCI UART driver: unacknowledged receive-error interrupt causes a permanent interrupt storm and CPU lockup

Noroxi assessment

Priority: Monitor (action score 18/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.15% (FIRST EPSS).
  • Physical access to the device is required. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: zephyrproject zephyr 4.3.2, 4.5.0.

Low priority for now. Upgrade to zephyrproject zephyr 4.3.2, 4.5.0 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

The Renesas RA SCI UART driver's receive-error ISR, uart_ra_sci_eri_isr() in drivers/serial/uart_renesas_ra_sci.c, acknowledged the error condition only when a Zephyr interrupt-driven callback had already been registered. With CONFIG_UART_INTERRUPT_DRIVEN=y and CONFIG_UART_ASYNC_API=n, if data->user_cb is NULL the ISR body is empty: the SCI error flags (SSR.ORER, SSR.FER, SSR.PER) are left set and the ICU event flag R_ICU->IELSR_b[eri_irq].IR is never cleared, so the interrupt re-pends immediately and the ISR is re-entered without end. The error interrupt is masked at boot by uart_ra_sci_init(), but FSP's R_SCI_UART_Open() unconditionally re-enables it, and uart_ra_sci_configure() - the back end of the public uart_configure() API, enabled by default via CONFIG_UART_USE_RUNTIME_CONFIGURE - performs a Close()/Open() pair without re-masking it. Any runtime uart_configure() therefore leaves the error interrupt live regardless of whether a callback has been set, as does calling uart_irq_err_enable() on its own. An instance used with the polling API, or the window between uart_configure() and uart_irq_callback_user_data_set(), thus runs with the error interrupt unmasked and no callback registered. The trigger is an ordinary receive line error - overrun, framing, parity, or a break condition - which is fully determined by the device attached to the serial link. A peer able to assert a break or transmit at a mismatched baud rate produces such an error at will, so a single frame is enough to enter the state. The impact is availability only: the CPU is captured in the re-entering ISR and never returns to thread context, hanging the entire system until an external reset or hardware watchdog fires. There is no memory corruption or information disclosure. Builds using the asynchronous UART API are unaffected, because the fall-through to FSP's sci_uart_eri_isr() clears both the error flags and the pending IRQ.

MediumCVSS 4.6 · v3.1—No exploit Fix available
Published
Nov 9, 2026
Updated
Nov 9, 2026
EPSS
0.1% · 4th percentile

Report tools

JSON

Action score

18

Monitor

Low priority for now.

CVSS
18 / 40 · 4.6 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CNA vs NVD score

NVD
—
CNA · zephyr
4.6
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (zephyr). Independent of NVD's CPE analysis and usually ahead of it.

  • zephyrproject zephyr

    • 4.0.0 and later · before 4.3.2affected · semver
    • 4.4.0 and later · before 4.5.0affected · semver

Same product

zephyrproject: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-4260Potential off-by-one buffer overflow vulnerability in the Zephyr FS subsystem
    40Plan
  • CVE-2021-3625Buffer overflow in Zephyr USB DFU DNLOAD
    40Plan
  • CVE-2020-10071Insufficient publish message length validation in MQTT
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-87044Nov 4, 2026 · Memory leak in the Mbed TLS crypto shim on failed cipher/AEAD operations leads to remotely triggered crypto denial of service
    26Monitor
  • ← EarlierCVE-2026-87045Nov 6, 2026 · NULL pointer dereference in the Zephyr HTTP/2 server when a header block is completed by a CONTINUATION frame
    30Monitor
  • Later →CVE-2026-90586Nov 9, 2026 · Xtensa MMU userspace: uninitialized thread page-table pointer leads to out-of-bounds supervisor-mode writes
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
zephyrproject zephyr4.3.2Vendor (CNA)
zephyrproject zephyr4.5.0Vendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 11, 2026+1 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-10686101 days apartMissing hop-limit decrement on IPv6 forwarding path allows unbounded packet looping (DoS) in Zephyr routers
    30Monitor
  • CVE-2025-2962503 days apartInfinite loop in dns_copy_qname
    30Monitor
  • CVE-2026-1223688 days apartInfinite loop (DoS) in Bluetooth GATT client parsing of Read-By-Type responses with zero data length
    26Monitor
  • CVE-2026-10642138 days apartUnbounded TX busy-loop DoS in Zephyr PL011 UART driver under CTS hardware flow control
    26Monitor
  • CVE-2026-4179238 days apartstm32: usb: Infinite while loop in Interrupt Handler
    24Monitor
  • CVE-2026-1592356 days apartInfinite loop denial of service in Zephyr SDIO byte-I/O from a card-supplied zero max_blk_size
    18Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Physical access to the device is required.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Physical
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-835 · Loop with Unreachable Exit Condition ('Infinite Loop')

CVSS vector

CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Exploit maturity— → none
  2. Fix✗ → ✓

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References

Show all references (1 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records