CVE-2020-8833Public exploit

Arbitrary file read via crash-report symlink race

Published Apr 22, 2020 · Updated Sep 16, 2024

TOCTOU race in Canonical Apport on affected Ubuntu releases allows local users to read arbitrary files through a symlink attack. The cron cleanup opens a zero-length crash report and later calls os.chown on its pathname, allowing replacement with a symlink between those operations. Exploitation requires local low-privileged access, a successful race, and fs.protected_symlinks disabled; Ubuntu's default value of 1 blocks this path.

CVSS severity5.6
Medium
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

TOCTOU race in Canonical Apport on affected Ubuntu releases allows local users to read arbitrary files through a symlink attack. The cron cleanup opens a zero-length crash report and later calls os.chown on its pathname, allowing replacement with a symlink between those operations. Exploitation requires local low-privileged access, a successful race, and fs.protected_symlinks disabled; Ubuntu's default value of 1 blocks this path.

The record

CVE
CVE-2020-8833
Published
Apr 22, 2020
Updated
Sep 16, 2024
Vendor
Canonical
Product
Apport
Classifications
CWE-367, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 22, 2020CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.20.11 <2.20.11-0ubuntu8.8 changes=[{"at":"2.20.11-0ubuntu22","status":"unaffected"}]
  2. Affected versionversion=2.20.1 <2.20.1-0ubuntu2.23
  3. Affected versionversion=2.20.9 <2.20.9-0ubuntu7.14

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Canonical · Apportversion=2.20.11 <2.20.11-0ubuntu8.8 changes=[{"at":"2.20.11-0ubuntu22","status":"unaffected"}]; version=2.20.1 <2.20.1-0ubuntu2.23; version=2.20.9 <2.20.9-0ubuntu7.14

Published CVSS scores

1.9NISTAV:L/AC:M/Au:N/C:P/I:N/A:N
4.7NISTCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
5.6Canonical Ltd.CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
T1068Exploitation for Privilege Escalation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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