Indexer denial-of-service via malformed S2S request

published 2022-03-25 4y ago modified 2026-06-17 4mo ago also EUVD-2021-26750

cvss: 7.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.6%; EPSS 0.6% chance of exploitation in 30 days, percentile 49%
public exploits: 0; none known

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.

Patch / fix

fixed in 1

splunk splunk 7.3.9, 8.0.9, 8.1.3

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Exploit prediction

0.60% chance of exploitation in the next 30 days, higher than 49% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD	2.0	4.3	AV:N/AC:M/Au:N/C:N/I:N/A:P

Affected products

Splunk Splunk Enterprise

Classification

Weakness

CWE-125 Out-of-bounds Read
CWE-20 Improper Input Validation

References

splunk.com /en_us/product-security/announcements/svd-2022-0301.html
vendor-advisory
claroty.com /2022/03/24/blog-research-locking-down-splunk-enterprise-indexers-and-forwarders/
third-party-advisory

Sources

CVE List CVE-2021-3422
NVD CVE-2021-3422

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