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Fencer Intel
medium 5.6

CVE-2020-8833 json

Apport race condition in crash report permissions

published 6y ago modified 4mo ago also EUVD-2020-29676

cvss
5.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 28%
public exploits
0
none known

Summary

Time-of-check Time-of-use Race Condition vulnerability on crash report ownership change in Apport allows for a possible privilege escalation opportunity. If fs.protected_symlinks is disabled, this can be exploited between the os.open and os.chown calls when the Apport cron script clears out crash files of size 0. A symlink with the same name as the deleted file can then be created upon which chown will be called, changing the file owner to root. 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-2020-8833

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

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Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • bugs.launchpad.net https://bugs.launchpad.net/ubuntu/+source/apport/+bug/1862933 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.6 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
NVD 3.1 4.7 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 1.9 AV:L/AC:M/Au:N/C:P/I:N/A:N

Affected products

  • Canonical Apport

Classification

Weakness
  • CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

References

Sources

Fencer Intel 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.