CVE-2021-3524Network attack vector

HTTP header injection via carriage-return handling

Published May 17, 2021 · Updated Aug 3, 2024

HTTP header injection in Red Hat Ceph Storage RadosGW before 14.2.21 allows remote attackers to alter CORS responses via crafted configuration. RGWCORSRule::format_exp_headers() escapes line feeds in ExposeHeader values but passes carriage returns into Access-Control-Expose-Headers. Exploitation requires a victim to make a CORS request while a crafted ExposeHeader value is present, enabling response-header modification without data disclosure or service interruption.

CVSS severity6.5
Medium
EPSS probability1.61%
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 Red Hat Ceph Storage RadosGW before 14.2.21 allows remote attackers to alter CORS responses via crafted configuration. RGWCORSRule::format_exp_headers() escapes line feeds in ExposeHeader values but passes carriage returns into Access-Control-Expose-Headers. Exploitation requires a victim to make a CORS request while a crafted ExposeHeader value is present, enabling response-header modification without data disclosure or service interruption.

The record

CVE
CVE-2021-3524
Published
May 17, 2021
Updated
Aug 3, 2024
Vendor
389 Directory Server
Product
Red Hat Ceph Storage
Classifications
CWE-74, CWE-20, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 17, 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=ceph 14.2.21

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

389 Directory Server · Red Hat Ceph Storageversion=ceph 14.2.21

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/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-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
CWE-20Improper Input Validation
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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