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SplunkApplication

CVE-2021-3422

HIGH · 7.5 CVSS v3.1 Published 2022-03-25
Fix available
A fix is available. Upgrade to 7.3.9 / 8.0.9 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

This is a denial-of-service vulnerability in Splunk Enterprise's Splunk-to-Splunk (S2S) protocol caused by missing validation of a key-value field. It affects Splunk Enterprise instances configured to index Universal Forwarder traffic, but does not impact the Universal Forwarders themselves. An unauthenticated remote attacker can crash the receiving Splunk instance by sending specially crafted S2S protocol data.

MitigationUpgrade to Splunk Enterprise 7.3.9, 8.0.9, 8.1.3 or later per the version matrix. Additionally, securing Splunk forwarding with TLS encryption or authentication tokens reduces exploitability and lowers severity to Medium.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
SplunkApplication
Affected:< 7.3.9>= 8.0, < 8.0.9>= 8.1, < 8.1.3

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm Splunk product type
    Run the command: splunk --version or check $SPLUNK_HOME/etc/splunk-launch.conf for the product type. This vulnerability affects Splunk Enterprise, NOT Universal Forwarders.
    Affected if The installed product is Splunk Enterprise (not Universal Forwarder)
  2. Check installed Splunk Enterprise version
    Run: splunk --version or access the Splunk web UI and navigate to About > Version to see the exact version number.
    Affected if Version is less than 7.3.9, OR between 8.0.0 and 8.0.8 inclusive, OR between 8.1.0 and 8.1.2 inclusive
  3. Verify S2S receiving configuration
    Check the inputs.conf file at $SPLUNK_HOME/etc/system/local/inputs.conf for [splunktcp] stanzas, which indicate the instance is configured to receive S2S (Splunk-to-Splunk) forwarded data.
    Affected if S2S receiving (splunktcp) is enabled and configured
  4. Confirm indexing of Universal Forwarder traffic
    Review the S2S configuration to determine if Universal Forwarders are sending data to this Splunk Enterprise instance. Check outputs.conf on forwarders or the receiving configuration in inputs.conf.
    Affected if This Splunk Enterprise instance indexes traffic from Universal Forwarders via S2S

A Splunk Enterprise instance is affected if it is version 7.3.x below 7.3.9, 8.0.x below 8.0.9, or 8.1.x below 8.1.3 AND it has S2S receiving enabled to index Universal Forwarder traffic.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 7.3.9 / 8.0.9 / 8.1.3 or later
Fixed in 7.3.98.0.98.1.3
Interim mitigation

Upgrade to Splunk Enterprise 7.3.9, 8.0.9, 8.1.3 or later per the version matrix. Additionally, securing Splunk forwarding with TLS encryption or authentication tokens reduces exploitability and lowers severity to Medium.

Recommended fix High confidence

Upgrade to Splunk Enterprise 7.3.9, 8.0.9, or 8.1.3 (or later) depending on your current major version branch

  1. Review Splunk upgrade documentation at docs.splunk.com for your current version and target version
  2. Ensure you have a complete backup of your Splunk environment including configuration files and the main index
  3. Test the upgrade in a non-production environment first
  4. Download the appropriate Splunk Enterprise fixed version (7.3.9, 8.0.9, or 8.1.3) from splunk.com
  5. Stop the Splunk Enterprise service before upgrading
  6. Install the upgrade using the Splunk installer for your operating system
  7. After upgrade, verify the Splunk service starts successfully
  8. Confirm the Splunk-to-Splunk protocol is functioning correctly
Caveat Standard Splunk upgrade considerations apply - review release notes for your target version for any feature changes or deprecated functionality

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Splunk Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-3422 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data