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CVE-2026-13216— Out-of-bounds stack write in Zephyr virtio PCI driver from unvalidated device-supplied capability length

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.

virtio PCI 驱动程序（drivers/virtio/virtio_pci.c）在驱动初始化期间会解析设备的 PCI 能力列表。在 函数中，设备提供的能力长度字节 （通过 从 PCI 配置空间读取）仅使用 进行检查。该断言在启用 时才会生效，而在生产构建中默认关闭，因此该值在到达复制逻辑时完全未经验证。 该长度随后用于驱动一个循环，将额外的能力双字（dwords）复制到调用者提供的固定大小栈缓冲区中。如果 小于基础结构体 的 24 字节，会导致无符号变量 发生下溢，接近 ，从而产生近乎无限的栈写入；如果 超

CVSS 6.1 · Medium

Affected Version Matrix 1

VendorProduct Version RangeStatus
zephyrproject zephyr 4.2.0< 4.4.2 affected
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I. Basic Information for CVE-2026-13216

Vulnerability Information
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Vulnerability Title
Out-of-bounds stack write in Zephyr virtio PCI driver from unvalidated device-supplied capability length
Source: CVE Program / CVE List V5
Vulnerability Description
The virtio PCI driver (drivers/virtio/virtio_pci.c) parses a device's PCI capability list during driver initialization. In virtio_pci_read_cap() the device-supplied capability length byte cap_len (read from PCI config space via pcie_conf_read()) was only checked with assert(tmp.cap_len == cap_struct_size). That assert resolves to __ASSERT_NO_MSG(), gated by CONFIG_ASSERT, which defaults off in production builds, so the value reached the copy logic completely unvalidated. The length then drives a loop that copies extra capability dwords into a fixed-size stack buffer supplied by the caller. A cap_len below the 24-byte base struct virtio_pci_cap underflows the unsigned extra_data_words count to a near-SIZE_MAX value, producing an effectively unbounded stack write; a cap_len above the caller's buffer (up to 255) writes up to roughly 228 bytes of device-controlled data past the buffer. Both are out-of-bounds writes of attacker-controlled content executed in kernel mode during boot-time device probe. The input originates from the virtio device. In the common deployment where Zephyr runs as a guest under a hypervisor, the device backend is the host, which already fully outranks the guest, so the bug yields no privilege escalation. The exploitable case is a virtio device that is untrusted relative to the Zephyr kernel — an untrusted or physical/passthrough virtio PCIe device on a bare-metal system, or a confidential-computing posture where the guest must defend against the host — where a malicious device can corrupt the kernel stack and potentially achieve code execution or a crash. The fix replaces the compiled-out assert with a runtime range check rejecting cap_len outside [sizeof(struct virtio_pci_cap), cap_struct_size] before any arithmetic or copy.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存写
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
zephyrproject zephyr 4.2.0 ~ 4.4.2 -

II. Public POCs for CVE-2026-13216

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III. Intelligence Information for CVE-2026-13216

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Patches & Fixes for CVE-2026-13216 (1)

Vendor Advisories for CVE-2026-13216 (1)

Same Patch Batch · zephyrproject · 2026-08-25 · 5 CVEs total

CVE-2026-13214 9.8 CRITICAL Stack buffer overflow in OCPP GetConfiguration key parsing
CVE-2026-13215 6.8 MEDIUM Zephyr ext2 mount: unvalidated superblock block size causes out-of-bounds write from a cra
CVE-2026-13217 5.9 MEDIUM NULL-pointer dereference in Zephyr OCPP CALLRESULT parsing via unchecked strtok_r/atoi
CVE-2026-13478 5.5 MEDIUM Out-of-bounds read in Zephyr ext2 block-bitmap validation from a crafted s_blocks_count

IV. Related Vulnerabilities

Same product: zephyr
Same vendor: zephyrproject
Same weakness: CWE-787

V. Comments for CVE-2026-13216

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