CVE-2021-31164Network attack vector

Log forgery via unsanitized request data

Published May 4, 2021 · Updated Aug 3, 2024

CRLF injection in Apache Unomi before 1.5.5 allows remote attackers to forge log entries through crafted request data. Multiple REST, servlet, scripting, persistence, and plug-in log statements pass request-derived values to Log4j without neutralizing carriage returns or line feeds. No authentication or user interaction is required, but the bounded impact is log-integrity loss rather than code execution or service interruption.

CVSS severity7.5
High
EPSS probability2.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CRLF injection in Apache Unomi before 1.5.5 allows remote attackers to forge log entries through crafted request data. Multiple REST, servlet, scripting, persistence, and plug-in log statements pass request-derived values to Log4j without neutralizing carriage returns or line feeds. No authentication or user interaction is required, but the bounded impact is log-integrity loss rather than code execution or service interruption.

The record

CVE
CVE-2021-31164
Published
May 4, 2021
Updated
Aug 3, 2024
Vendor
The Apache Software Foundation
Product
Apache Unomi
Classifications
CWE-93, CWE-74, T1565.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 4, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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 Unomi <1.5.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache Unomiversion=Apache Unomi <1.5.5

Published CVSS scores

7.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
5.0NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:N/I:P/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-93Improper Neutralization of CRLF Sequences ('CRLF Injection')
CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
T1565.001Stored Data Manipulation

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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