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CVE-2026-13478— Out-of-bounds read in Zephyr ext2 block-bitmap validation from a crafted s_blocks_count

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.

以下是该漏洞描述信息的中文翻译： Zephyr 的 ext2 文件系统驱动在 函数中（位于 ）通过计算 并将结果传递给 来验证磁盘上的块位图（block bitmap）。然而，该辅助函数（位于 ）将其参数视为位的数量，并以每 8 位读取一个字节的方式处理位图。实际上，位图缓冲区（ ）仅是一个获取的磁盘块，大小仅为 字节（即最多 位）。 和 直接从超级块中获取，且未与该单组的容量上限进行边界检查。 仅验证魔数（magic）、修订版本（revision）和块大小移位（block-size shift），但未对块计数进行

CVSS 5.5 · Medium

Affected Version Matrix 1

VendorProduct Version RangeStatus
zephyrproject zephyr 3.5.0< 4.4.2 affected
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I. Basic Information for CVE-2026-13478

Vulnerability Information
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Vulnerability Title
Out-of-bounds read in Zephyr ext2 block-bitmap validation from a crafted s_blocks_count
Source: CVE Program / CVE List V5
Vulnerability Description
The Zephyr ext2 filesystem driver validates the on-disk block bitmap in ext2_init_fs() (subsys/fs/ext2/ext2_impl.c) by passing fs_blocks = s_blocks_count - s_first_data_block to ext2_bitmap_count_set(). That helper (subsys/fs/ext2/ext2_bitmap.c) treats its argument as a number of bits and reads one bitmap byte per eight bits, but the bitmap buffer (BGROUP_BLOCK_BITMAP) is a single fetched block of only fs->block_size bytes (capacity fs->block_size * 8 bits). s_blocks_count and s_first_data_block are taken verbatim from the superblock and were never bounded against this single-group capacity; ext2_verify_disk_superblock() checks the magic, revision, and block-size shift but not the block count. A crafted ext2 image with an oversized s_blocks_count (up to ~4 billion, against a maximum 4096-byte block / 32768-bit bitmap) makes ext2_bitmap_count_set() scan roughly 512 MB of memory past the bitmap block — a large out-of-bounds read of the static block slab and adjacent memory. The defect is reached during mount: ext2_init_fs() is invoked from ext2_mount() (subsys/fs/ext2/ext2_ops.c), the registered .mount operation. Any path that mounts an attacker-supplied ext2 image (removable media, a disk/flash partition, or a downloaded image) triggers it. The kernel-privileged parser operates on attacker-controlled data, so the bug is exploitable wherever untrusted ext2 media can be mounted. Impact is an out-of-bounds read only: the resulting bit count is compared internally and the mount is rejected, so no attacker-controlled bytes are returned (not a useful information leak). The ~512 MB over-read will almost certainly cross an unmapped or MPU-protected boundary and fault, crashing the system — a denial of service triggered by mounting a single malformed image. The fix rejects any image whose fs_blocks exceeds fs->block_size * 8 before the scan.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存读
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
zephyrproject zephyr 3.5.0 ~ 4.4.2 -

II. Public POCs for CVE-2026-13478

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III. Intelligence Information for CVE-2026-13478

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Patches & Fixes for CVE-2026-13478 (1)

Vendor Advisories for CVE-2026-13478 (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-2026-13216 6.1 MEDIUM Out-of-bounds stack write in Zephyr virtio PCI driver from unvalidated device-supplied cap
CVE-2026-13217 5.9 MEDIUM NULL-pointer dereference in Zephyr OCPP CALLRESULT parsing via unchecked strtok_r/atoi

IV. Related Vulnerabilities

Same product: zephyr
Same vendor: zephyrproject
Same weakness: CWE-125

V. Comments for CVE-2026-13478

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