CVE-2026-87043

Что произошло

The entropy-device random number generator in subsys/random/random_entropy_device.c returned early with -ENODEV from rand_get() as soon as device_is_ready() failed, before reaching the non-cryptographic system-timer fallback further down the same function. Because z_impl_sys_rand_get() returns void and discards that error — and the public sys_rand_get() syscall is itself declared void, so it cannot report failure — the caller's output buffer was left untouched and its previous contents were handed back as random data. The thin wrappers make this a plain uninitialized read: sys_rand32_get() declares uint32_t ret;, calls sys_rand_get(&ret, sizeof(ret)) and returns ret. The "not ready" state is a normal runtime condition rather than a fault. Entropy drivers initialise at PRE_KERNEL_1 with CONFIG_ENTROPY_INIT_PRIORITY (default 50), so any earlier initialiser — kernel objects run at priority 30 — observes an unready device; the sibling generator subsys/random/random_xoshiro128.c and z_early_rand_get() in kernel/init.c both already carried an explicit timer fallback for exactly this case. The state is also permanent for the boot when an entropy driver's init hook fails, which several in-tree drivers can do on real hardware (entropy_stm32 on an RNG clock configuration error, entropy_psa_crypto when psa_crypto_init() fails, entropy_nrf_cracen, entropy_esp32, entropy_virtio). When this occurs, every non-cryptographic random value in the system is either a constant or stale memory. coap_next_token() in subsys/net/lib/coap/coap.c fills a static buffer, so every CoAP token becomes the same .bss constant; tcp_init_isn() in subsys/net/ip/tcp.c returns an uninitialized stack word as the TCP initial sequence number; DHCPv4/DHCPv6 transaction IDs, WebSocket masking keys and RTP SSRCs are similarly degraded, and arch/arm64/core/pac.c derives per-thread Pointer Authentication keys from the same source. Where the bytes are transmitted directly — SSH packet padding, the netmidi2 session nonce, a DTLS connection ID on builds without CONFIG_CSPRNG_ENABLED — stale caller stack or heap contents are disclosed on the wire. The fix initialises ret to -ENODEV and only calls entropy_get_entropy() when the device is ready, so the not-ready case now falls through to the timer fallback and the buffer is always written. The cryptographically secure path is unchanged: sys_csrand_get() still propagates the error to the caller and never silently degrades. An attacker cannot induce the unready state, but can observe and exploit the resulting non-random values remotely on an affected device.

Что делать

dpkg-query -W -f='${Package}	${Version}\n'

rpm -qa --qf '%{NAME}\t%{VERSION}-%{RELEASE}\n'

Get-HotFix | Select-Object HotFixID, InstalledOn

Продукты и затронутые версии

{
  "status": "affected",
  "version": "4.4.0",
  "lessThan": "4.5.0",
  "versionType": "semver"
}

CVSS: оценки и векторы

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

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

Источники и ссылки

{
  "cwes": [
    "cve",
    "nvd"
  ],
  "title": {
    "source": "cve",
    "received_at": "2026-11-04T06:19:42.266792+00:00"
  },
  "scores": [
    "cve",
    "nvd"
  ],
  "status": {
    "source": "cve",
    "received_at": "2026-11-04T06:19:42.266792+00:00"
  },
  "affected": [
    "cve"
  ],
  "published": {
    "source": "cve",
    "received_at": "2026-11-04T06:19:42.266792+00:00"
  },
  "solutions": [],
  "references": [
    "cve",
    "nvd"
  ],
  "description": {
    "source": "cve",
    "received_at": "2026-11-04T06:19:42.266792+00:00"
  },
  "workarounds": [],
  "configurations": []
}

Хронология записи

1. Появились сведения об исправлении04.11.2026, 09:19
2. Опубликована04.11.2026, 09:19

Личная заметка и статус

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