VulnerabilityPublished 19 Mar 2026

CVE-2026-21788: HCLSoftware Connections · Cross-site Scripting

Affects HCLSoftware ConnectionsSource CVE Database V5

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Not known to be exploited · CVSS 5.4 Medium.

Data as of 30 Oct 2026, 20:25 UTC

CVSS 3.1 base score

5.4Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

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

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 19 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
HCLSoftwareConnections	Affected =8	Fixed in–

AI-suggested

Organizations should immediately review their deployment of HCL Connections version 8 and apply any available patches or updates from HCL Software once released. In the absence of patches, implement strict input validation and output encoding on all user-supplied data to prevent script injection. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers. Educate users to be cautious about clicking untrusted links or opening suspicious content within the platform. Monitor logs for unusual activities indicative of XSS exploitation attempts. Consider deploying web application firewalls (WAFs) with rules tailored to detect and block XSS payloads targeting HCL Connections. Regularly audit and review user privileges to minimize the impact of compromised accounts. Finally, maintain up-to-date backups and incident response plans to quickly address any breaches.

Description

HCL Connections is vulnerable to a cross-site scripting attack where an attacker may leverage this issue to execute arbitrary script code in the browser of an unsuspecting user which leads to executing malicious script code. This may allow the attacker steal cookie-based authentication credentials and comprise user's account then launch other attacks.

Impact

The primary impact of this vulnerability is the potential compromise of user accounts through theft of authentication cookies, which can lead to unauthorized access to sensitive collaboration data and internal communications. This can facilitate lateral movement within an organization, data exfiltration, and further targeted attacks. The vulnerability undermines user trust and may expose organizations to compliance and regulatory risks if sensitive information is leaked. Because HCL Connections is often deployed in enterprise environments for internal collaboration, exploitation could disrupt business operations and damage reputations. Although no availability impact is noted, the confidentiality and integrity risks are significant enough to warrant attention. The requirement for user interaction and limited privileges reduces the likelihood of widespread automated exploitation but does not eliminate targeted attack risks.

Summary

CVE-2026-21788 is a cross-site scripting (XSS) vulnerability identified in HCL Software Connections version 8. The root cause is improper neutralization of user-supplied input during web page generation, classified under CWE-79. This flaw enables an attacker to inject malicious script code that executes within the context of a victim user's browser session. Successful exploitation requires the attacker to have limited privileges (PR:L) and the victim to interact with crafted content (UI:R), such as clicking a malicious link or viewing a manipulated page. The vulnerability impacts confidentiality and integrity by allowing theft of cookie-based authentication tokens, which can lead to session hijacking and unauthorized actions within the application. The attack vector is network-based (AV:N), meaning the attacker can exploit it remotely without physical access. The vulnerability does not affect availability. No public exploits or active exploitation campaigns have been reported as of the publication date. The CVSS 3.1 score of 5.4 reflects a medium severity level, balancing ease of exploitation with limited scope of impact. The vulnerability is particularly relevant for organizations using HCL Connections 8 for collaboration and social networking within enterprise environments.

CWE-79Improper Neutralization of Input During Web Page Generation (Cross-site Scripting) (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #1OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation · Architecture and Design
Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages.
Architecture and Design · Implementation · Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide…
OWASP Cheat Sheets
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Injection Prevention (opens in a new tab)
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
OWASP ASVS 4.0.3
V5.3.3 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
XSS Using MIME Type Mismatch (opens in a new tab)
DOM-Based XSS (opens in a new tab)
Reflected XSS (opens in a new tab)
Stored XSS (opens in a new tab)
Cross-Site Scripting (XSS) (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

support.hcl-software.com/csm?id=kb_article&sysparm_article=KB0129107 (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 19 Mar 2026, 09:24 UTC

WeaknessesCWE-79

Technical details

References

Community reviews

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