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CVE-2026-15923— Infinite loop denial of service in Zephyr SDIO byte-I/O from a card-supplied zero max_blk_size

Quick assessment

Affected
zephyrproject zephyr
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

zephyrproject Zephyr是zephyrproject组织开源的一款面向物联网设备的实时操作系统。 zephyrproject Zephyr 3.6.0版本至4.4.2之前版本存在资源管理错误漏洞，该漏洞源于subsys/sd/sdio.c中SDIO子系统函数sdio_io_rw_extended_helper()使用字节I/O循环且未验证从SDIO卡CIS FUNCE元组解码的max_blk_size，当最大块大小为0时循环步长始终为0，导致无限自旋并在持有互斥锁时永不释放，可能造成SDI

CVSS 4.6 · Medium EPSS 0.23% · P14

Affected Version Matrix 1

VendorProduct Version RangeStatus
zephyrproject zephyr 3.6.0< 4.4.2 affected
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I. Basic Information for CVE-2026-15923

Vulnerability Information
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Vulnerability Title
Infinite loop denial of service in Zephyr SDIO byte-I/O from a card-supplied zero max_blk_size
Source: CVE Program / CVE List V5
Vulnerability Description
The Zephyr SDIO subsystem function sdio_io_rw_extended_helper() in subsys/sd/sdio.c finishes transfers with a byte-I/O loop that uses size = MIN(remaining, func->cis.max_blk_size) as the per-iteration step. The value func->cis.max_blk_size is decoded directly from the SDIO card's CIS FUNCE tuple in sdio_decode_cis() and is not validated. When a card reports a maximum block size of zero, size is always 0, remaining never decreases, and the loop spins forever. The loop is reached from the public SDIO client API used by drivers, including sdio_read_fifo(), sdio_write_fifo(), and the incrementing register read/write helpers, each of which enters the loop while holding the per-card mutex func->card->lock. A card advertising max_blk_size == 0 therefore hangs the calling thread permanently on its first non-block-aligned transfer and never releases the mutex, denying service to the SDIO peripheral (and any subsystem such as Wi-Fi that depends on it) until the device is reset. The malicious value must come from the SDIO card itself, so the defect is exploitable where a removable SDIO/combo card slot lets an attacker insert a crafted or malfunctioning card (a physical attack vector); on boards with a soldered SDIO peripheral it is not attacker-influenceable. There is no memory-safety, confidentiality, or integrity impact — only a permanent availability loss. The fix returns -EIO when func->cis.max_blk_size is zero, before the loop is entered.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
不可达退出条件的循环(无限循环)
Source: CVE Program / CVE List V5
Vulnerability Title
zephyrproject Zephyr 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
zephyrproject Zephyr是zephyrproject组织开源的一款面向物联网设备的实时操作系统。 zephyrproject Zephyr 3.6.0版本至4.4.2之前版本存在资源管理错误漏洞，该漏洞源于subsys/sd/sdio.c中SDIO子系统函数sdio_io_rw_extended_helper()使用字节I/O循环且未验证从SDIO卡CIS FUNCE元组解码的max_blk_size，当最大块大小为0时循环步长始终为0，导致无限自旋并在持有互斥锁时永不释放，可能造成SDI
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
zephyrproject zephyr 3.6.0 ~ 4.3.2 -

II. Public POCs for CVE-2026-15923

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III. Intelligence Information for CVE-2026-15923

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Patches & Fixes for CVE-2026-15923 (1)

Vendor Advisories for CVE-2026-15923 (1)

Same Patch Batch · zephyrproject · 2026-09-14 · 6 CVEs total

CVE-2026-16147 6.8 MEDIUM it82xx2 USB device controller submits incomplete OUT transfer buffers, causing use-after-f
CVE-2026-14986 6.8 MEDIUM Out-of-bounds write in it51xxx I2C target FIFO ISR on oversized write transaction
CVE-2026-15893 6.5 MEDIUM Zephyr IPv6 Neighbor Discovery zero reachable time from crafted Router Advertisement cause
CVE-2026-15924 5.9 MEDIUM Use-after-free / double-free from unsynchronized concurrent access to the TLS client sessi
CVE-2026-16148 4.6 MEDIUM Kernel panic in the it82xx2 USB device controller driver via re-initialization of a busy d

IV. Related Vulnerabilities

Same product: zephyr
Same vendor: zephyrproject
Same weakness: CWE-835