7

CVE-2018-18955: canonical ubuntu_linux Incorrect Authorization

CVSS: 7.0v3.0HighModified
AliasesUBUNTU-CVE-2018-18955DEBIAN-CVE-2018-18955
Published 16-11-2018Last modified 05-08-2024
Open JSON

Vulnerability summary

CVE-2018-18955 is a high (CVSS 7.0) Incorrect Authorization vulnerability in canonical ubuntu_linux. EPSS estimates a 7.61% chance of exploitation in the next 30 days, higher than 94.5% of scored vulnerabilities. 7 public exploits are recorded.

Overall risk
40/100
0100
Medium · default modelHow is this calculated?
CVSS score
7.0/10
010
High · v3.0 (NVD)
EPSS score
7.61%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits7exploit-database, metasploit

Advisory lineage

Upstream 0 · Downstream 3 · Related 3
USN-3833-1USN-3836-1USN-3836-2

Timeline

  1. 16-11-2018
    PublishedVulnerability first disclosed.
  2. 05-08-2024
    Last modifiedVulnerability information updated.

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 metrics

4 scores · 3 sources · 2 versions

EPSS trend

Probability

7.61%

Chance of exploitation in the next 30 days

Percentile

95%

Versus all other CVEs

30-day change

0.00 pp

From 7.61% on 19-09-2026

19-09-202619-10-2026
EPSS score
7.61%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

7 found
  • exploit-databaselocallinuxVerified

    Linux - Broken uid/gid Mapping for Nested User Namespaces

    Maturity: weaponized

  • exploit-databaselocallinuxVerified

    Linux - Nested User Namespace idmap Limit Local Privilege Escalation (Metasploit)

    Maturity: weaponized

  • exploit-databaselocallinuxUnverified

    Linux Kernel 4.15.x < 4.19.2 - 'map_write() CAP_SYS_ADMIN' Local Privilege Escalation (cron Method)

    Maturity: poc

Show all 7 exploits
  • exploit-databaselocallinuxUnverified

    Linux Kernel 4.15.x < 4.19.2 - 'map_write() CAP_SYS_ADMIN' Local Privilege Escalation (dbus Method)

    Maturity: poc

  • exploit-databaselocallinuxUnverified

    Linux Kernel 4.15.x < 4.19.2 - 'map_write() CAP_SYS_ADMIN' Local Privilege Escalation (ldpreload Method)

    Maturity: poc

  • exploit-databaselocallinuxUnverified

    Linux Kernel 4.15.x < 4.19.2 - 'map_write() CAP_SYS_ADMIN' Local Privilege Escalation (polkit Method)

    Maturity: poc

  • MetasploitMetasploitremoteVerified

    Linux Nested User Namespace idmap Limit Local Privilege Escalation

    exploit/linux/local/nested_namespace_idmap_limit_priv_esc

    Maturity: weaponized

Weaknesses

CWE · root cause

Affected systems

Ubuntu8 products
  • linux< 4.15.0-42.45
  • linux-aws< 4.15.0-1029.30
  • linux-azure< 4.15.0-1035.36~14.04.2 | < 4.15.0-1035.36~16.04.1 | < 4.15.0-1035.36
  • linux-gcp< 4.15.0-1025.26~16.04.1 | < 4.15.0-1025.26
  • linux-hwe< 4.15.0-42.45~16.04.1
Canonical1 product
Debian1 product
  • linux< 4.18.20-1
Linux1 product

4 vendors · 11 products

References

23 links
Show all 23 references