CVE-2020-15703: There is no input validation on the Locale property in an apt transaction

Routine

MEDIUM 4.0DOWNGRADE

CVE-2020-15703 is a medium-severity flaw (CVSS 4.0) affecting aptdaemon. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

There is no input validation on the Locale property in an apt transaction. An unprivileged user can supply a full path to a writable directory, which lets aptd read a file as root. Having a symlink in place results in an error message if the file exists, and no error otherwise. This way an unprivileged user can check for the existence of any files on the system as root.

Why this priority

Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	4.0 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 58%)
CISA exploited list	No
Weakness	CWE-22
Published	2020-10-31
Last modified	2026-06-17

Publisher (CNA): Canonical Ltd. · Vendor: aptdaemon project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-10-31 04:15 UTCPublished CVE record published
2026-06-17 02:57 UTCUpdated Record last modified

aptdaemon project aptdaemon DOWNGRADE

Affected: 1.1.1 bzr982-0ubuntu14.4 · 1.1.1 bzr982-0ubuntu19.4 · 1.1.1 bzr982-0ubuntu32.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.1.1

1. Check installed version

apt-cache policy aptdaemon || rpm -q aptdaemon || aptdaemon --version

2. No fixed release: DOWNGRADE to a release before 1.1.1 (Debian / Ubuntu)

apt-cache madison aptdaemon sudo apt install aptdaemon=<VERSION_BEFORE_1.1.1> sudo apt-mark hold aptdaemon

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list aptdaemon sudo dnf downgrade aptdaemon-<VERSION_BEFORE_1.1.1> sudo dnf versionlock add aptdaemon

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-15703?

aptdaemon: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-15703 being exploited?

CVE-2020-15703 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-15703 affect?

CVE-2020-15703 affects aptdaemon. Severity is medium (CVSS 4.0). There is no input validation on the Locale property in an apt transaction. An unprivileged user can supply a full path to a writable directory, which lets aptd read a file as root. Having a symlink in place results in an error message if th

How urgent is CVE-2020-15703?

Priority 30/100. Public exploit reference

References

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