CVE-2020-18703: XML External Entities (XXE) in Quokka v0.4.0 allows remote attackers to execute arbitrary code via the compone

This week

CRITICAL 9.8REMOTEDOWNGRADE

CVE-2020-18703 is a critical-severity flaw (CVSS 9.8) affecting quokka. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

XML External Entities (XXE) in Quokka v0.4.0 allows remote attackers to execute arbitrary code via the component 'quokka/utils/atom.py'.

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

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

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.8% (top 14%)
CISA exploited list	No
Weakness	CWE-611
Published	2021-08-16
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: quokka project

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

Am I affected?

Timeline

2021-08-16 18:15 UTCPublished CVE record published
2026-06-17 02:59 UTCUpdated Record last modified

quokka project quokka DOWNGRADE

Affected: 0.4.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.4.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 0.4.0 (Debian / Ubuntu)

apt-cache madison quokka sudo apt install quokka=<VERSION_BEFORE_0.4.0> sudo apt-mark hold quokka

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

dnf --showduplicates list quokka sudo dnf downgrade quokka-<VERSION_BEFORE_0.4.0> sudo dnf versionlock add quokka

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-2020-18703?

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

Is CVE-2020-18703 being exploited?

CVE-2020-18703 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-2020-18703 affect?

CVE-2020-18703 affects quokka. Severity is critical (CVSS 9.8). XML External Entities (XXE) in Quokka v0.4.0 allows remote attackers to execute arbitrary code via the component 'quokka/utils/atom.py'.

How urgent is CVE-2020-18703?

Priority 66/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2020-18705 CRITICAL 9.8 DOWNGRADE XML External Entities (XXE) in Quokka v0.4.0 allows remote attackers to execute arbitrary code via the compone
CVE-2020-18702 MEDIUM 6.1 DOWNGRADE Cross Site Scripting (XSS) in Quokka v0.4.0 allows remote attackers to execute arbitrary code via the 'Usernam

References

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