VulnerabilityPublished 21 Apr 2026

CVE-2026-40497: freescout · Cross-site Scripting

Affects freescoutSource CVE Database V5

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Not known to be exploited · CVSS 8.1 High : upgrade to 1.8.213 soon.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 3.1 base score

8.1High

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 15% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.8.213

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: High
User Interaction: Required
Scope: Changed
Confidentiality: High
Integrity: High
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: High: The attacker is authorized with (i.e., requires) privileges that provide significant (e.g., administrative) control over the vulnerable component that could affect component-wide settings and files.
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: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to 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 21 Apr 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 29 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

Upgrade freescout and freescout-help-desk/freescout to 1.8.213.

Affected software

Product	Affected	Fixed in
freescout-help-deskfreescout	Affected <1.8.213	Fixed in 1.8.213
GitHubfreescout-help-desk/freescout`pkg:github/freescout-help-desk/freescout`Other threats	Affected <1.8.213	Fixed in 1.8.213

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade FreeScout to version 1.8.213 or later, which contains the updated fix that properly addresses the incomplete sanitization of the mailbox signature field. Until upgraded, restrict mailbox settings access to trusted users only, as exploitation requires such permissions. Patch status is not explicitly stated in the advisory fields, but the description confirms version 1.8.213 contains the fix.

Description

FreeScout versions prior to 1.8.213 contain a cross-site scripting (XSS) vulnerability due to improper sanitization of the mailbox signature field. The vulnerability arises because the sanitization function removes certain dangerous tags but does not remove <style> tags, allowing CSS injection. An attacker with mailbox settings access can inject CSS that exfiltrates CSRF tokens from other agents or admins viewing the mailbox, enabling privilege escalation. This issue is a partial regression of a previous fix and is addressed in version 1.8.213.

Impact

An attacker with agent-level mailbox settings permissions can exploit this vulnerability to inject malicious CSS that steals CSRF tokens from administrators or other agents viewing mailbox conversations. This enables the attacker to perform unauthorized state-changing actions with elevated privileges, such as creating admin accounts or modifying credentials, leading to privilege escalation. The vulnerability does not impact availability but has high confidentiality and integrity impacts.

Summary

CVE-2026-40497 is a high-severity cross-site scripting vulnerability in FreeScout help desk software versions before 1.8.213. The vulnerability stems from the Helper::stripDangerousTags() function, which removes script, form, iframe, and object tags but fails to strip <style> tags from the mailbox signature field. Because the mailbox signature is saved and later rendered unescaped in conversation views, and the Content Security Policy allows unsafe inline styles, an attacker with mailbox settings access can inject CSS attribute selectors that exfiltrate CSRF tokens from other users viewing the mailbox. With these tokens, the attacker can perform privileged actions, including creating admin accounts or changing credentials, effectively escalating privileges from agent to admin. The issue is a result of an incomplete fix for a prior XSS vulnerability (GHSA-jqjf-f566-485j). The vulnerability is fixed in FreeScout version 1.8.213.

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

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 28 Apr 2026, 06:07 UTC

WeaknessesCWE-79

Technical details

References

Community reviews

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