Vulnerability Description
In the Linux kernel 4.15.x through 4.19.x before 4.19.2, map_write() in kernel/user_namespace.c allows privilege escalation because it mishandles nested user namespaces with more than 5 UID or GID ranges. A user who has CAP_SYS_ADMIN in an affected user namespace can bypass access controls on resources outside the namespace, as demonstrated by reading /etc/shadow. This occurs because an ID transformation takes place properly for the namespaced-to-kernel direction but not for the kernel-to-namespaced direction.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Linux | Linux Kernel | >= 4.15, < 4.19.2 |
| Canonical | Ubuntu Linux | 16.04 |
Related Weaknesses (CWE)
References
- http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d2f007PatchVendor Advisory
- http://www.securityfocus.com/bid/105941Third Party AdvisoryVDB Entry
- https://bugs.chromium.org/p/project-zero/issues/detail?id=1712PatchThird Party Advisory
- https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.18.19PatchVendor Advisory
- https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.19.2PatchVendor Advisory
- https://github.com/torvalds/linux/commit/d2f007dbe7e4c9583eea6eb04d60001e85c6f1bPatchVendor Advisory
- https://security.netapp.com/advisory/ntap-20190416-0003/
- https://support.f5.com/csp/article/K39103040
- https://usn.ubuntu.com/3832-1/Third Party Advisory
- https://usn.ubuntu.com/3833-1/Third Party Advisory
- https://usn.ubuntu.com/3835-1/Third Party Advisory
- https://usn.ubuntu.com/3836-1/Third Party Advisory
- https://usn.ubuntu.com/3836-2/Third Party Advisory
- https://www.exploit-db.com/exploits/45886/ExploitPatchThird Party Advisory
- https://www.exploit-db.com/exploits/45915/ExploitThird Party AdvisoryVDB Entry
FAQ
What is CVE-2018-18955?
CVE-2018-18955 is a vulnerability with a CVSS score of 7.0 (HIGH). In the Linux kernel 4.15.x through 4.19.x before 4.19.2, map_write() in kernel/user_namespace.c allows privilege escalation because it mishandles nested user namespaces with more than 5 UID or GID ran...
How severe is CVE-2018-18955?
CVE-2018-18955 has been rated HIGH with a CVSS base score of 7.0/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2018-18955?
Check the references section above for vendor advisories and patch information. Affected products include: Linux Linux Kernel, Canonical Ubuntu Linux.