CVE-2026-10645 Out-of-bounds read in Zephyr ext2 directory entry traversal from a crafted filesystem image
A crafted ext2 filesystem image triggers an out-of-bounds read in Zephyr, leaking kernel heap memory and causing denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-10645?
CVE-2026-10645 is a medium-severity memory corruption vulnerability in Zephyrproject Zephyr, published on 22 Jun 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
The Zephyr ext2 filesystem driver (subsys/fs/ext2) trusted the on-disk directory entry fields de_rec_len and de_name_len when walking a directory block. ext2_fetch_direntry() guarded only with de_name_len > EXT2_MAX_FILE_NAME, but de_name_len is a uint8_t and EXT2_MAX_FILE_NAME is 255, so the check is always false; the function then memcpy'd up to 255 name bytes and the lookup/readdir paths advanced traversal by an unvalidated de_rec_len. Each directory block is read into a block_size-sized slab buffer, and block_off can be driven near the block end by preceding entries' rec_len, so the 8-byte header read and the subsequent name memcpy can read up to ~263 bytes past the end of the block buffer into adjacent heap/slab memory. On the readdir path those bytes are returned to the caller in fs_dirent.name, leaking adjacent kernel heap memory; a de_rec_len of 0 also causes a zero-progress infinite loop (denial of service), and the unlink path's memmove(de, next, next_reclen) over unvalidated records is an additional OOB read/write source. The defect is reached by any path-based operation (open, stat, unlink, rename, mkdir) or directory listing on a mounted ext2 volume, so a crafted or corrupted ext2 image on attacker-supplied storage (SD card, USB mass storage, or otherwise mounted image) triggers it. Affected: Zephyr ext2 from its introduction in v3.5.0 through v4.4.0. The fix validates rec_len and name_len in the parser and rejects entries whose header does not fit the remaining block or whose rec_len crosses the block boundary in every traversal caller.
Weakness: CWE-125
Which versions are affected by CVE-2026-10645?
It affects 1 product.
Products include Zephyrproject Zephyr.
How do I fix CVE-2026-10645?
No fix has been published for CVE-2026-10645 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-10645 being exploited?
There is no known exploitation of CVE-2026-10645 in the wild and no public exploit code.
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Sources
Also known as GHSA-hwrh-9h3x-vccm, UBUNTU-CVE-2026-10645.