CVE-2021-20802Network attack vector

Authenticated data modification via HTTP header injection

Published Oct 13, 2021 · Updated Aug 3, 2024

HTTP header injection in Cybozu Remote Service 3.1.8 through 3.1.9 allows remote authenticated users to alter stored product information. Cybozu identifies the communication functionality but has not disclosed the handler, input field, or incorrect operation that permits injected header data to be stored. Basic authenticated access is required, and the published impact is limited to modification without reported disclosure or service interruption.

CVSS severity5.3
Medium
EPSS probability0.99%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTTP header injection in Cybozu Remote Service 3.1.8 through 3.1.9 allows remote authenticated users to alter stored product information. Cybozu identifies the communication functionality but has not disclosed the handler, input field, or incorrect operation that permits injected header data to be stored. Basic authenticated access is required, and the published impact is limited to modification without reported disclosure or service interruption.

The record

CVE
CVE-2021-20802
Published
Oct 13, 2021
Updated
Aug 3, 2024
Vendor
Cybozu
Product
Cybozu Remote Service
Classifications
CWE-113, CWE-74, T1565.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 13, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=3.1.8 to 3.1.9

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Cybozu · Cybozu Remote Serviceversion=3.1.8 to 3.1.9

Published CVSS scores

5.3NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-113Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')
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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