CVE-2026-90833: Zephyr out-of-bounds write in EEPROM (high)

Summary

The simulated EEPROM driver validated access ranges in eeprom_range_is_valid() (drivers/eeprom/eeprom_simulator.c) with a single test, (offset + len) <= config->size. Because offset is a signed off_t and len an unsigned size_t of the same rank, the addition is evaluated in unsigned arithmetic: a negative offset combined with a compensating len wraps the sum back into the accepted range. eeprom_sim_read() and eeprom_sim_write() then memcpy() through the EEPROM(addr) macro, which is plain pointer arithmetic on the driver's static mock_eeprom array, so the copy addresses memory located before that array.

eeprom_read() and eeprom_write() are __syscall entry points, and their verification handlers in drivers/eeprom/eeprom_handlers.c check only the device object and the caller's own data buffer (K_SYSCALL_MEMORY_READ/K_SYSCALL_MEMORY_WRITE) — the offset argument is passed to the driver unvalidated. With CONFIG_USERSPACE=y, a CONFIG_EEPROM_SIMULATOR device instance, and the device object granted to a user thread (the usage the in-tree tests/drivers/eeprom/api suite exercises from ZTEST_USER threads), an unprivileged thread could supply a negative offset and have the kernel perform the copy on its behalf.

The result is an out-of-bounds read of kernel .bss returned into the caller's buffer and, via the write path, an out-of-bounds write of caller-supplied bytes over kernel memory preceding mock_eeprom. Both the start address and the length of the affected span are attacker-selected, so the primitive is sufficient to corrupt adjacent kernel state and escape the user-mode sandbox. Exposure is limited to builds that instantiate the simulated EEPROM (status = "okay" by default on qemu_x86 and native_sim, otherwise added by a devicetree overlay) together with userspace isolation.

The fix rejects negative offsets and performs the remaining bound check without overflow.

cve.now Index

8Pcve.now Index 8 of 100 · methodology v3 · provisional

Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
Exposure?/25Unknown. No advisory context yet
Reach?/20Unknown. No tracked technology or package matched
Severity7.8/10CVSS 7.8
No patch0/5No signal

What would change the score

Would score about 63 if added to CISA KEV
Would score about 58 if CISA's SSVC rates exploitation active
Would score about 30 if advisories confirm default setups are exposed

How the score works · Rankings

What to do

Upgrade to a fixed version: 4.3.2, 4.5.0.

Check your systems with an agent

Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.

Check whether my systems are affected by CVE-2026-90833 (Signed offset bypasses bounds check in simulated EEPROM driver, allowing out-of-bounds kernel memory read and write from user mode), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-90833 (entry last updated 2026-11-10):
Affected:
- zephyrproject zephyr: from 2.2.0, fixed in 4.3.2; from 4.4.0, fixed in 4.5.0
Fixed versions: 4.3.2, 4.5.0.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-90833 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-90833 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/zephyrproject-rtos/zephyr/commit/ce2ec9b3a34d71f52f5d1d7491b91393e334713e
- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-vf6j-hcx8-44vh
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Entry: https://cve.now/CVE-2026-90833
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-90833.

Timeline

Nov 10, 2026, 10:07 PM UTCCVE published
Nov 10, 2026, 10:23 PM UTCFirst seen by cve.now

Affected versions

zephyr
From 2.2.0 · fixed in 4.3.2; From 4.4.0 · fixed in 4.5.0

Evidence 4

Vendor advisory · 1

Establishes: Affected and fixed versions.

Advisory
GitHub · zephyrproject-rtos/zephyr · Advisory GHSA-vf6j-hcx8-44vh

CVE record · 2

Establishes: The identifier and description.

Record
CVE List · CVE-2026-90833
Record
NVD · CVE-2026-90833

Corrections

None so far.

Something wrong on this page? Report an error. Every fix is listed here.

Questions about CVE-2026-90833

Is CVE-2026-90833 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data

Which versions are affected by CVE-2026-90833?

zephyr: from 2.2.0 before 4.3.2; from 4.4.0 before 4.5.0.Source: cve.now feed data

How do I fix CVE-2026-90833?

Upgrade to a fixed version: 4.3.2, 4.5.0.Source: cve.now feed data

Signed offset bypasses bounds check in simulated EEPROM driver, allowing out-of-bounds kernel memory read and write from user mode