The NXP MCUX TRNG entropy driver in drivers/entropy/entropy_mcux_trng.c passed the caller's byte count straight to the…
Summary
Out-of-bounds write reported (CVE-2026-19736). Successful exploitation can lead to full system takeover.
Original description
The description as published by the source.
The NXP MCUX TRNG entropy driver in drivers/entropy/entropy_mcux_trng.c passed the caller's byte count straight to the vendor SDK routine TRNG_GetRandomData(). On i.MX RT5xx and RT6xx parts the SDK compiles its TRNG_SW_HEALTH_TESTS variant, which always copies whole 32-bit words and draws entropy rounded up to a multiple of 128 bytes. Its "caller buffer is full" guard tests dataSize == 0, so a request whose length is not a multiple of four makes dataSize underflow past zero and the SDK keeps writing into the caller's buffer for the entire extraction: a 1-byte request results in 128 bytes written, and any non-word-multiple length overflows by up to 127 bytes.
entropy_get_entropy() is a syscall, and its verifier in drivers/entropy/entropy_handlers.c validates only the requested length via K_SYSCALL_MEMORY_WRITE(). With CONFIG_USERSPACE enabled, an unprivileged user-mode thread that has merely been granted the entropy device can therefore choose both the destination address and a length such as 1, and cause the kernel to write up to 127 bytes beyond the region it proved it owns. On these Cortex-M33 targets there is no MMU, so user partitions and kernel data share one SRAM and the overflow can land in adjacent kernel state. The same defect is reached from kernel mode by any caller requesting a non-word-multiple length, including getentropy() and, in builds where sys_csrand_get()/sys_rand_get() resolve to the hardware generator, sys_rand8_get() and sys_rand16_get().
Impact is me…
Source: NIST National Vulnerability Database NVD
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-19736 has been found.
Successful exploitation can lead to full system takeover. CVSS score: 7.8/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "CVE-2026-19736" on the vendor's site.
CVE-2026-19736 — CWE-787 / CVSS v3 7.8
Attack vector: local / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Out-of-bounds write (CWE-787) has been reported.
Check the vendor advisory for the affected versions.
Severity: High (CVSS 7.8/10). Successful exploitation can lead to full system takeover.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで影響コンポーネントを特定する。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。