4.6
MEDIUM CVSS 3.1
CVE-2026-15923
Infinite loop denial of service in Zephyr SDIO byte-I/O from a card-supplied zero max_blk_size
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.

INFO

Published Date :

Sept. 14, 2026, 5:17 p.m.

Last Modified :

Sept. 14, 2026, 5:17 p.m.

Remotely Exploit :

No
Affected Products

The following products are affected by CVE-2026-15923 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Zephyrproject zephyr
2 Zephyrproject zephyr
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.
Score Version Severity Vector Exploitability Score Impact Score Source
CVSS 3.1 MEDIUM e2e69745-5e70-4e92-8431-deb5529a81ad
CVSS 3.1 MEDIUM MITRE-CVE
CVSS 3.1 MEDIUM [email protected]
Solution
Fix denial of service by checking max block size before I/O.
  • Update the SDIO subsystem to check for zero max block size.
  • Return an error code when max block size is zero.
  • Prevent infinite loop execution in I/O transfers.
  • Apply the vendor-provided fix to the SDIO driver.
References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2026-15923.

URL Resource
https://github.com/zephyrproject-rtos/zephyr/commit/3b2f7aaee1f2ca52904c7e7f028951ba39456abd
https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-4pvm-wrcp-jjf5
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-15923 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-15923 weaknesses.

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2026-15923 vulnerability anywhere in the article.

The following table lists the changes that have been made to the CVE-2026-15923 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • New CVE Received by [email protected]

    Sep. 14, 2026

    Action Type Old Value New Value
    Added 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.
    Added CVSS V3.1 AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
    Added CWE CWE-835
    Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/15xxx/CVE-2026-15923.json">CVE-2026-15923</a>
    Added Reference https://github.com/zephyrproject-rtos/zephyr/commit/3b2f7aaee1f2ca52904c7e7f028951ba39456abd
    Added Reference https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-4pvm-wrcp-jjf5
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.