CVE-2020-15864: An issue was discovered in Quali CloudShell 9.3

This month

MEDIUM 6.1DOWNGRADE

CVE-2020-15864 is a medium-severity flaw (CVSS 6.1) affecting cloudshell. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in Quali CloudShell 9.3. An XSS vulnerability in the login page allows an attacker to craft a URL, with a constructor.constructor substring in the username field, that executes a payload when the user visits the /Account/Login page.

Why this priority

Public exploit reference

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

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.7% (top 47%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-01-17
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: quali

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

Am I affected?

Timeline

2021-01-17 20:15 UTCPublished CVE record published
2026-06-17 02:57 UTCUpdated Record last modified

quali cloudshell DOWNGRADE

Affected: 9.3

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.3

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 9.3 (Debian / Ubuntu)

apt-cache madison cloudshell sudo apt install cloudshell=<VERSION_BEFORE_9.3> sudo apt-mark hold cloudshell

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

dnf --showduplicates list cloudshell sudo dnf downgrade cloudshell-<VERSION_BEFORE_9.3> sudo dnf versionlock add cloudshell

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-2020-15864?

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

Is CVE-2020-15864 being exploited?

CVE-2020-15864 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-2020-15864 affect?

CVE-2020-15864 affects cloudshell. Severity is medium (CVSS 6.1). An issue was discovered in Quali CloudShell 9.3. An XSS vulnerability in the login page allows an attacker to craft a URL, with a constructor.constructor substring in the username field, that executes a payload when the user visits the /Acc

How urgent is CVE-2020-15864?

Priority 40/100. Public exploit reference

Related CVEs

CVE-2017-9767 MEDIUM 5.4 UPGRADE Multiple cross-site scripting (XSS) vulnerabilities in Quali CloudShell before 8 allow remote authenticated us

References

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