CVE-2021-43185Network attack vector

Remote URL redirection via unvalidated Host header

Published Nov 9, 2021 · Updated Aug 4, 2024

Host header injection in JetBrains YouTrack before 2021.3.23639 allows remote attackers to influence generated URLs via crafted HTTP Host headers. The request-processing logic accepts the untrusted Host value when constructing redirects or links instead of validating it against an allowed host, enabling attacker-controlled URL generation. The network-reachable flaw requires no authentication; available advisories describe URL redirection impact but do not document data access, code execution, or service interruption.

CVSS severity9.8
Critical
EPSS probability2.01%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Host header injection in JetBrains YouTrack before 2021.3.23639 allows remote attackers to influence generated URLs via crafted HTTP Host headers. The request-processing logic accepts the untrusted Host value when constructing redirects or links instead of validating it against an allowed host, enabling attacker-controlled URL generation. The network-reachable flaw requires no authentication; available advisories describe URL redirection impact but do not document data access, code execution, or service interruption.

The record

CVE
CVE-2021-43185
Published
Nov 9, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-601, CWE-74
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 9, 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

9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P

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.

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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-601URL Redirection to Untrusted Site ('Open Redirect')
CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

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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