LiteSpeed Cache <= 7.9 - Reflected Cross-Site Scripting via ESI 'esi' Parameter

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-76579
StatePUBLISHED
AssignerWordfence
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-19 09:16:34 UTC
Updated2026-09-21 13:33:33 UTC
DescriptionThe LiteSpeed Cache plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the 'esi' parameter in all versions up to, and including, 7.9 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link. Exploitation requires that the attacker supply a validly signed 'esi' value in the GET query string while submitting a separate attacker-controlled 'esi' payload as a POST body field, relying on PHP's default $_REQUEST merge order to have the POST value take precedence at the point of execution.

Risk And Classification

Primary CVSS: v3.1 4.7 MEDIUM from [email protected]

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

EPSS: 0.002300000 probability, percentile 0.141100000 (date 2026-09-22)

Problem Types: CWE-79 | CWE-79 CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary4.7MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N
3.1CNADECLARED4.7MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Litespeedtech LiteSpeed Cache affected 7.9 semver Not specified

References

ReferenceSourceLinkTags
plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/changeset/3676856/litespeed-cache/trunk/src/esi.cls.php [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/changeset [email protected] plugins.trac.wordpress.org
www.wordfence.com/threat-intel/vulnerabilities/id/ba236f86-0434-4030-8e14-4db39... [email protected] www.wordfence.com
plugins.trac.wordpress.org/browser/litespeed-cache/tags/7.9/src/esi.cls.php [email protected] plugins.trac.wordpress.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: mak3bread (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-08-19T14:18:31.000ZVendor Notified
CNA2026-09-18T19:46:10.000ZDisclosed

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