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Fencer Vulns
medium 6.5

CVE-2020-8831 json

World writable root owned lock file created in user controllable location

published 2020-04-22 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-29674

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 51%
public exploits
0
none known

Summary

Apport creates a world writable lock file with root ownership in the world writable /var/lock/apport directory. If the apport/ directory does not exist (this is not uncommon as /var/lock is a tmpfs), it will create the directory, otherwise it will simply continue execution using the existing directory. This allows for a symlink attack if an attacker were to create a symlink at /var/lock/apport, changing apport's lock file location. This file could then be used to escalate privileges, for example. Fixed in versions 2.20.1-0ubuntu2.23, 2.20.9-0ubuntu7.14, 2.20.11-0ubuntu8.8 and 2.20.11-0ubuntu22.

Patch / fix

  • Canonical Apport 2.20.1-0ubuntu2.23, 2.20.9-0ubuntu7.14, 2.20.11-0ubuntu8.8, 2.20.11-0ubuntu22
  • apport Ubuntu 16.04 LTS 2.20.1-0ubuntu2.23
  • apport Ubuntu 18.04 LTS 2.20.9-0ubuntu7.14
  • apport Ubuntu 20.04 LTS 2.20.11-0ubuntu22
  • apport Ubuntu Pro 14.04 LTS 2.14.1-0ubuntu3.29+esm4

ubuntu advisories UBUNTU-CVE-2020-8831

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Exploit prediction

0.65% chance of exploitation in the next 30 days, higher than 51% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • launchpad.net https://launchpad.net/bugs/1862348 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
NVD 2.0 2.1 AV:L/AC:L/Au:N/C:N/I:P/A:N

Affected products

  • Canonical Apport

Classification

Weakness
  • CWE-379 Creation of Temporary File in Directory with Insecure Permissions
  • CWE-59 Improper Link Resolution Before File Access

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.