CVE-2021-33880: The aaugustin websockets library before 9.1 for Python has an Observable Timing Discrepancy on servers when HT

This month

MEDIUM 5.9REMOTEUPGRADEDOWNGRADEDOWNGRADE

CVE-2021-33880 is a medium-severity flaw (CVSS 5.9) affecting websockets, communications cloud native core policy, communications cloud native core security edge protection proxy. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The aaugustin websockets library before 9.1 for Python has an Observable Timing Discrepancy on servers when HTTP Basic Authentication is enabled with basic_auth_protocol_factory(credentials=...). An attacker may be able to guess a password via a timing attack.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	2.3% (top 17%)
CISA exploited list	No
Weakness	CWE-203
Published	2021-06-06
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: oracle · websockets project

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

Am I affected?

Timeline

2021-06-06 15:15 UTCPublished CVE record published
2026-06-17 03:55 UTCUpdated Record last modified

websockets project websockets UPGRADE

Affected: < 9.1

Fixed in: 9.1

Safe to downgrade to: no unaffected older release

1. Check installed version

pip show websockets

2. UPGRADE to 9.1

pip install --upgrade "websockets>=9.1"

oracle communications cloud native core policy DOWNGRADE

Affected: 1.14.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.14.0

1. Check installed version

apt-cache policy communications-cloud-native-core-policy || rpm -q communications-cloud-native-core-policy || communications-cloud-native-core-policy --version

2. No fixed release: DOWNGRADE to a release before 1.14.0 (Debian / Ubuntu)

apt-cache madison communications-cloud-native-core-policy sudo apt install communications-cloud-native-core-policy=<VERSION_BEFORE_1.14.0> sudo apt-mark hold communications-cloud-native-core-policy

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

dnf --showduplicates list communications-cloud-native-core-policy sudo dnf downgrade communications-cloud-native-core-policy-<VERSION_BEFORE_1.14.0> sudo dnf versionlock add communications-cloud-native-core-policy

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.

oracle communications cloud native core security edge protection proxy DOWNGRADE

Affected: 1.5.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.5.0

1. Check installed version

apt-cache policy communications-cloud-native-core-security-edge-protection-proxy || rpm -q communications-cloud-native-core-security-edge-protection-proxy || communications-cloud-native-core-security-edge-protection-proxy --version

2. No fixed release: DOWNGRADE to a release before 1.5.0 (Debian / Ubuntu)

apt-cache madison communications-cloud-native-core-security-edge-protection-proxy sudo apt install communications-cloud-native-core-security-edge-protection-proxy=<VERSION_BEFORE_1.5.0> sudo apt-mark hold communications-cloud-native-core-security-edge-protection-proxy

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

dnf --showduplicates list communications-cloud-native-core-security-edge-protection-proxy sudo dnf downgrade communications-cloud-native-core-security-edge-protection-proxy-<VERSION_BEFORE_1.5.0> sudo dnf versionlock add communications-cloud-native-core-security-edge-protection-proxy

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.

oracle communications cloud native core service communication proxy DOWNGRADE

Affected: 1.14.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.14.0

1. Check installed version

apt-cache policy communications-cloud-native-core-service-communication-proxy || rpm -q communications-cloud-native-core-service-communication-proxy || communications-cloud-native-core-service-communication-proxy --version

2. No fixed release: DOWNGRADE to a release before 1.14.0 (Debian / Ubuntu)

apt-cache madison communications-cloud-native-core-service-communication-proxy sudo apt install communications-cloud-native-core-service-communication-proxy=<VERSION_BEFORE_1.14.0> sudo apt-mark hold communications-cloud-native-core-service-communication-proxy

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

dnf --showduplicates list communications-cloud-native-core-service-communication-proxy sudo dnf downgrade communications-cloud-native-core-service-communication-proxy-<VERSION_BEFORE_1.14.0> sudo dnf versionlock add communications-cloud-native-core-service-communication-proxy

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.

oracle communications cloud native core unified data repository DOWNGRADE

Affected: 1.14.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.14.0

1. Check installed version

apt-cache policy communications-cloud-native-core-unified-data-repository || rpm -q communications-cloud-native-core-unified-data-repository || communications-cloud-native-core-unified-data-repository --version

2. No fixed release: DOWNGRADE to a release before 1.14.0 (Debian / Ubuntu)

apt-cache madison communications-cloud-native-core-unified-data-repository sudo apt install communications-cloud-native-core-unified-data-repository=<VERSION_BEFORE_1.14.0> sudo apt-mark hold communications-cloud-native-core-unified-data-repository

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

dnf --showduplicates list communications-cloud-native-core-unified-data-repository sudo dnf downgrade communications-cloud-native-core-unified-data-repository-<VERSION_BEFORE_1.14.0> sudo dnf versionlock add communications-cloud-native-core-unified-data-repository

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-2021-33880?

websockets: upgrade to 9.1; communications cloud native core policy: downgrade or apply the listed mitigation; communications cloud native core security edge protection proxy: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-33880 being exploited?

CVE-2021-33880 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-2021-33880 affect?

CVE-2021-33880 affects websockets, communications cloud native core policy, communications cloud native core security edge protection proxy. Severity is medium (CVSS 5.9). The aaugustin websockets library before 9.1 for Python has an Observable Timing Discrepancy on servers when HTTP Basic Authentication is enabled with basic_auth_protocol_factory(credentials=...). An attacker may be able to guess a password

How urgent is CVE-2021-33880?

Priority 46/100. Remotely exploitable, no login, no user action

Software pages

Python vulnerabilities

Related CVEs

CVE-2018-1000518 HIGH 7.5 DOWNGRADE aaugustin websockets version 4 contains a CWE-409: Improper Handling of Highly Compressed Data (Data Amplifica

References

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