Vulnerabilities
Misconfiguration
Compliance
CVE Vulnerabilities

CVE-2019-11481

Improper Link Resolution Before File Access ('Link Following')

Published: Feb 08, 2020 | Modified: Nov 21, 2024
CVSS 3.x
7.8
HIGH
Source:
NVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS 2.x
6.1 MEDIUM
AV:L/AC:L/Au:N/C:C/I:P/A:P
RedHat/V2
RedHat/V3
Ubuntu
LOW
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Additional information
NVDhttps://nvd.nist.gov/vuln/detail/CVE-2019-11481
CWEhttps://cwe.mitre.org/data/definitions/59.html

Kevin Backhouse discovered that apport would read a user-supplied configuration file with elevated privileges. By replacing the file with a symbolic link, a user could get apport to read any file on the system as root, with unknown consequences.

Weakness

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

Affected Software

NameVendorStart VersionEnd Version
Ubuntu_linuxCanonical14.04 (including)14.04 (including)
Ubuntu_linuxCanonical16.04 (including)16.04 (including)
Ubuntu_linuxCanonical18.04 (including)18.04 (including)
Ubuntu_linuxCanonical19.04 (including)19.04 (including)
Ubuntu_linuxCanonical19.10 (including)19.10 (including)
ApportUbuntubionic*
ApportUbuntudevel*
ApportUbuntudisco*
ApportUbuntueoan*
ApportUbuntuesm-infra-legacy/trusty*
ApportUbuntuesm-infra/bionic*
ApportUbuntuesm-infra/xenial*
ApportUbuntutrusty*
ApportUbuntutrusty/esm*
ApportUbuntuxenial*

Potential Mitigations

  • Follow the principle of least privilege when assigning access rights to entities in a software system.
  • Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

References

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