CVE-2026-26993VulnerabilityPublished 20 Feb 2026Updated 23 Feb 2026

CVE-2026-26993: FlintSH Flare · Cross-site Scripting

Affects FlintSH FlareSource CVE Database V5

Not known to be exploited · CVSS 4.6 Medium · fixed in 1.7.1 : update FlintSH Flare when convenient.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

4.6Medium

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 25% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.7.1

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: Required
Scope: Unchanged
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: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
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 20 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 2026-10-25.

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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC 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
FlintSHFlare	Affected =1.7.1	Fixed in–

AI-suggested

To mitigate CVE-2026-26993, organizations should immediately upgrade FlintSH Flare to version 1.7.1 or later, where the vulnerability has been fixed. Beyond patching, administrators should implement strict content validation policies that restrict or sanitize uploads of active content formats such as SVG, HTML, and XML, especially when these files can be rendered or viewed in raw mode. Employing Content Security Policy (CSP) headers can help limit the impact of any residual script execution by restricting the sources of executable scripts. Additionally, user education to avoid opening suspicious or unexpected files in raw mode can reduce the risk of exploitation. Monitoring and logging file uploads and access patterns may help detect attempts to exploit this vulnerability. Finally, restricting upload permissions to trusted users and enforcing strong authentication controls will reduce the attack surface.

Description

Flare is a Next.js-based, self-hostable file sharing platform that integrates with screenshot tools. Versions 1.7.0 and below allow users to upload files without proper content validation or sanitization. By embedding malicious JavaScript within an SVG (or other active content formats such as HTML or XML), an attacker can achieve script execution in the context of the application's origin when a victim views the file in “raw” mode. This results in a stored Cross-Site Scripting (XSS) vulnerability that can be exploited to exfiltrate user data. This issue has been fixed in version 1.7.1.

Impact

The primary impact of CVE-2026-26993 is the potential compromise of user confidentiality and integrity within affected FlintSH Flare deployments. Successful exploitation allows attackers to execute arbitrary JavaScript in the context of the application, potentially leading to theft of sensitive information such as authentication tokens, personal data, or other confidential files accessible through the platform. This can facilitate further attacks like session hijacking or privilege escalation. Although the vulnerability does not directly affect system availability, the breach of trust and data confidentiality can have severe reputational and operational consequences for organizations relying on Flare for secure file sharing. Since exploitation requires authenticated access and user interaction, the risk is somewhat mitigated but remains significant in environments with multiple users or where attackers can coerce victims to view malicious files. Organizations with sensitive data or regulatory compliance requirements are particularly at risk. The vulnerability's presence in a self-hosted platform means that organizations managing their own Flare instances must proactively apply patches to avoid exposure.

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 Feb 2026, 13:30 UTC

WeaknessesCWE-79

Technical details

References

Community reviews

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