CVE-2021-3422
Indexer denial-of-service via malformed S2S request
The lack of validation of a key-value field in the Splunk-to-Splunk protocol results in a denial-of-service in Splunk Enterprise instances configured to index Universal Forwarder traffic. The vulnerability impacts Splunk Enterprise versions before 7.3.9, 8.0 versions before 8.0.9, and 8.1 versions before 8.1.3. It does not impact Universal Forwarders. When Splunk forwarding is secured using TLS or a Token, the attack requires compromising the certificate or token, or both. Implementation of either or both reduces the severity to Medium.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
7.5
Indexer denial-of-service via malformed S2S request
The lack of validation of a key-value field in the Splunk-to-Splunk protocol results in a denial-of-service in Splunk Enterprise instances configured to index Universal Forwarder traffic. The vulnerability impacts Splunk Enterprise versions before 7.3.9, 8.0 versions before 8.0.9, and 8.1 versions before 8.1.3. It does not impact Universal Forwarders. When Splunk forwarding is secured using TLS or a Token, the attack requires compromising the certificate or token, or both. Implementation of either or both reduces the severity to Medium.
- Record
CVE-2021-3422- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-125
- Updated
- 2026-11-02
EUVDEUVD-2021-26750
7.5
The lack of validation of a key-value field in the Splunk-to-Splunk protocol results in a denial-of-service in Splunk Enterprise instances configured to index Universal Forwarder traffic. The vulnerability impacts Splunk Enterprise versions before 7.3.9, 8.0 versions before 8.0.9, and 8.1 versions before 8.1.3. It does not impact Universal Forwarders. When Splunk forwarding is secured using TLS or a Token, the attack requires compromising the certificate or token, or both. Implementation of either or both reduces the severity to Medium.
- Record
EUVD-2021-26750- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-4c93-wvp2-c39r
7.5
The lack of validation of a key-value field in the Splunk-to-Splunk protocol results in a denial...
The lack of validation of a key-value field in the Splunk-to-Splunk protocol results in a denial-of-service in Splunk Enterprise instances configured to index Universal Forwarder traffic. See https://docs.splunk.com/Documentation/Splunk/latest/Forwarding/Enableareceiver for more information on configuring an indexer to listen for UF traffic. It does not impact Universal Forwarders. When Splunk forwarding is secured using TLS or a Token, the attack requires compromising the certificate or token, or both. As a partial mitigation and a security best practice, see https://docs.splunk.com/Documentation/Splunk/latest/Security/ConfigureSplunkforwardingtousesignedcertificates and https://docs.splunk.com/Documentation/Forwarder/latest/Forwarder/Controlforwarderaccess. Implementation of either or both reduces the severity to Medium.
- Record
GHSA-4c93-wvp2-c39r- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-20
- Updated
- 2026-11-02
NVD
7.5
The lack of validation of a key-value field in the Splunk-to-Splunk protocol results in a denial-of-service in Splunk Enterprise instances configured to index Universal Forwarder traffic. The vulnerability impacts Splunk Enterprise versions before 7.3.9, 8.0 versions before 8.0.9, and 8.1 versions before 8.1.3. It does not impact Universal Forwarders. When Splunk forwarding is secured using TLS or a Token, the attack requires compromising the certificate or token, or both. Implementation of either or both reduces the severity to Medium.
- Record
CVE-2021-3422- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - CVSS 2.0
- 4.3 Medium
AV:N/AC:M/Au:N/C:N/I:N/A:P - Weakness
- CWE-125, CWE-20
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-3422 is a high vulnerability (CVSS 7.5) in Splunk, published March 25, 2022. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.60%, the 49th percentile. No source names a fixed version.
References
splunk.com/en_us/product-security/announcements/svd-2022-0301.html
claroty.com/2022/03/24/blog-research-locking-down-splunk-enterprise-indexers-and-forwarders
nvd.nist.gov/vuln/detail/CVE-2021-3422
claroty.com/2022/03/24/blog-research-locking-down-splunk-enterprise-indexers-and-forwarders/2
github.com/advisories/GHSA-4c93-wvp2-c39r