CVE-2021-33880Network attack vector

HTTP Basic Auth password recovery via timing discrepancy

Published Jun 6, 2021 · Updated Aug 4, 2024

Observable timing discrepancy in Python websockets 8.0 through 9.0.2 allows remote attackers to recover HTTP Basic Auth passwords. The basic_auth_protocol_factory credential checker compares attacker-supplied passwords with ordinary equality, so response time varies with matching prefixes. Exploitation requires a server configured with credentials and repeated network measurements; successful guessing exposes the protected WebSocket service.

CVSS severity5.9
Medium
EPSS probability2.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Observable timing discrepancy in Python websockets 8.0 through 9.0.2 allows remote attackers to recover HTTP Basic Auth passwords. The basic_auth_protocol_factory credential checker compares attacker-supplied passwords with ordinary equality, so response time varies with matching prefixes. Exploitation requires a server configured with credentials and repeated network measurements; successful guessing exposes the protected WebSocket service.

The record

CVE
CVE-2021-33880
Published
Jun 6, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-208, CWE-203, T1110.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.9NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
8.2GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA: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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-208Observable Timing Discrepancy
CWE-203Observable Discrepancy
T1110.001Password Guessing

Public exploit references

No public exploit references are available in this record.

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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