CVE-2021-38153Network attack vector

Credential recovery via variable-time secret comparison

Published Sep 22, 2021 · Updated Aug 4, 2024

Timing side channel in Apache Kafka 2.0.0 through 2.6.2, 2.7.0 through 2.7.1, and 2.8.0 enables remote credential guessing. Affected password- and key-validation paths call Arrays.equals, which stops at the first mismatch instead of examining the entire secret. Repeated unauthenticated network guesses can reveal partial-match information and reduce the work needed to recover a valid password or key.

CVSS severity5.9
Medium
EPSS probability6.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Timing side channel in Apache Kafka 2.0.0 through 2.6.2, 2.7.0 through 2.7.1, and 2.8.0 enables remote credential guessing. Affected password- and key-validation paths call Arrays.equals, which stops at the first mismatch instead of examining the entire secret. Repeated unauthenticated network guesses can reveal partial-match information and reduce the work needed to recover a valid password or key.

The record

CVE
CVE-2021-38153
Published
Sep 22, 2021
Updated
Aug 4, 2024
Vendor
The Apache Software Foundation
Product
Apache Kafka
Classifications
CWE-203, T1110
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 22, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Apache Kafka 2.0.x <=2.0.1
  2. Affected versionversion=Apache Kafka 2.1.x <=2.1.1
  3. Affected versionversion=Apache Kafka 2.2.x <=2.2.2
  4. Affected versionversion=Apache Kafka 2.3.x <=2.3.1
  5. Affected versionversion=Apache Kafka 2.4.x <=2.4.1
  6. Affected versionversion=Apache Kafka 2.5.x <=2.5.1
  7. Affected versionversion=Apache Kafka 2.6.x <=2.6.2
  8. Affected versionversion=Apache Kafka 2.7.x <=2.7.1
  9. Affected versionversion=Apache Kafka 2.8.x <=2.8.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache Kafkaversion=Apache Kafka 2.0.x <=2.0.1; version=Apache Kafka 2.1.x <=2.1.1; version=Apache Kafka 2.2.x <=2.2.2; version=Apache Kafka 2.3.x <=2.3.1; version=Apache Kafka 2.4.x <=2.4.1; version=Apache Kafka 2.5.x <=2.5.1; version=Apache Kafka 2.6.x <=2.6.2; version=Apache Kafka 2.7.x <=2.7.1; version=Apache Kafka 2.8.x <=2.8.0

Published CVSS scores

5.9GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A: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-203Observable Discrepancy
T1110Brute Force

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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