kernel: Privilege escalation in map_write() in kernel/user_namespace.c
Published Nov 16, 2018
7.8
HIGHCVSS 3.0
EPSS 7.61%
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.
Affected products
No data.
Configuration 1
- ≥ 4.15 · < 4.19.2
Configuration 2
- 16.04
- 18.04
- 18.10
No data.
Red Hat Enterprise Linux 5
kernel
Not affected
Red Hat Enterprise Linux 6
kernel
Not affected
Red Hat Enterprise Linux 7
kernel
Not affected
Red Hat Enterprise Linux 7
kernel-alt
Not affected
Red Hat Enterprise Linux 7
kernel-rt
Not affected
Red Hat Enterprise Linux 8
kernel
Not affected
Red Hat Enterprise Linux 8
kernel-rt
Not affected
Red Hat Enterprise MRG 2
kernel-rt
Not affected
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 5 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 6 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 7 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 7 | kernel-alt | Not affected | n/a |
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | n/a |
| Red Hat Enterprise Linux 8 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 8 | kernel-rt | Not affected | n/a |
| Red Hat Enterprise MRG 2 | kernel-rt | Not affected | n/a |
No package ranges for this CVE.
Remediation
Red Hat statement
This issue does not affect the Linux kernel versions as shipped with Red Hat Enterprise Linux 5, 6 and 7 because they did not include the commit that introduced this issue. This issue does not affect Red Hat Enterprise Linux 8 because the fix for this issue has not been included since the Red Hat Enterprise Linux 8 release.
Metrics
No CVSS v4.0 score for this CVE.
No CVSS v3.1 score for this CVE.
CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
1 other source (Red Hat) ▾
CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
AV:L/AC:M/Au:N/C:P/I:P/A:P
This CVE is not in the KEV list.
No CISA SSVC assessment for this CVE yet.
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 2, 2026.
Score over time
2021–2026- EPSS v1
- EPSS v2
- EPSS v3
- EPSS v4
- EPSS v5
Percentile over time
- EPSS v1
- EPSS v2
- EPSS v3
- EPSS v4
- EPSS v5
Table of values (30 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 2, 2026 | 7.61% (0.07611) | 94.38th | v5 (v2026.06.15) |
| Sep 22, 2026 | 7.61% (0.07611) | 94.28th | v5 (v2026.06.15) |
| Sep 21, 2026 | 17.30% (0.17303) | 97.03th | v5 (v2026.06.15) |
| Sep 6, 2026 | 7.61% (0.07611) | 94.15th | v5 (v2026.06.15) |
| Sep 5, 2026 | 17.30% (0.17303) | 96.96th | v5 (v2026.06.15) |
| Aug 30, 2026 | 7.61% (0.07611) | 94.12th | v5 (v2026.06.15) |
| Aug 28, 2026 | 17.30% (0.17303) | 96.94th | v5 (v2026.06.15) |
| Aug 24, 2026 | 7.61% (0.07611) | 94.08th | v5 (v2026.06.15) |
| Aug 23, 2026 | 17.30% (0.17303) | 96.93th | v5 (v2026.06.15) |
| Jun 15, 2026 | 7.61% (0.07611) | 93.76th | v5 (v2026.06.15) |
| Apr 20, 2026 | 9.57% (0.09568) | 92.88th | v4 (v2025.03.14) |
| Nov 21, 2025 | 12.22% (0.12220) | 93.56th | v4 (v2025.03.14) |
| Nov 18, 2025 | 7.32% (0.07324) | 90.77th | v4 (v2025.03.14) |
| Aug 11, 2025 | 11.25% (0.11246) | 93.22th | v4 (v2025.03.14) |
| Aug 8, 2025 | 10.09% (0.10093) | 92.77th | v4 (v2025.03.14) |
| Jul 17, 2025 | 8.72% (0.08716) | 92.07th | v4 (v2025.03.14) |
| Jun 4, 2025 | 10.27% (0.10266) | 92.75th | v4 (v2025.03.14) |
| Mar 17, 2025 | 8.81% (0.08806) | 91.89th | v4 (v2025.03.14) |
| Dec 12, 2024 | 0.11% (0.00109) | 45.63th | v3 (v2023.03.01) |
| Nov 10, 2023 | 0.11% (0.00109) | 43.72th | v3 (v2023.03.01) |
| Mar 7, 2023 | 0.09% (0.00093) | 38.10th | v3 (v2023.03.01) |
| Mar 6, 2023 | 12.63% (0.12625) | 95.53th | v2 (v2022.01.01) |
| May 13, 2022 | 12.63% (0.12625) | 95.22th | v2 (v2022.01.01) |
| Apr 1, 2022 | 13.15% (0.13151) | 95.31th | v2 (v2022.01.01) |
| Feb 4, 2022 | 13.15% (0.13151) | 90.52th | v2 (v2022.01.01) |
| Feb 3, 2022 | 52.93% (0.52930) | 99.08th | v1 |
| Sep 16, 2021 | 52.93% (0.52930) | 99.68th | v1 |
| Sep 14, 2021 | 13.21% (0.13208) | 96.12th | v1 |
| Sep 1, 2021 | 52.93% (0.52930) | 99.68th | v1 |
| Apr 14, 2021 | 52.93% (0.52930) | 0.00th | v1 |
References (20)
- http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd x_refsource_MISCPatchVendor Advisory
- http://www.securityfocus.com/bid/105941 vdb-entryx_refsource_BIDThird Party AdvisoryVDB Entry
- https://access.redhat.com/security/cve/CVE-2018-18955 Vendor Advisory
- https://bugs.chromium.org/p/project-zero/issues/detail?id=1712 x_refsource_MISCPatchThird Party Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1651384 Issue Tracking
- https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.18.19 x_refsource_MISCPatchVendor Advisory
- https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.19.2 x_refsource_MISCPatchVendor Advisory
- https://github.com/torvalds/linux/commit/d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd x_refsource_MISCPatchVendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2018-18955
- https://seclists.org/oss-sec/2018/q4/150
- https://security.netapp.com/advisory/ntap-20190416-0003/ x_refsource_CONFIRM
- https://support.f5.com/csp/article/K39103040 x_refsource_CONFIRM
- https://usn.ubuntu.com/3832-1/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://usn.ubuntu.com/3833-1/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://usn.ubuntu.com/3835-1/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://usn.ubuntu.com/3836-1/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://usn.ubuntu.com/3836-2/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://www.cve.org/CVERecord?id=CVE-2018-18955
- https://www.exploit-db.com/exploits/45886/ exploitx_refsource_EXPLOIT-DBPatchThird Party AdvisoryVDB Entry
- https://www.exploit-db.com/exploits/45915/ exploitx_refsource_EXPLOIT-DBThird Party AdvisoryVDB Entry
Change history (0)
No recorded changes yet.