VulnerabilityPublished 18 Jul 2025

CVE-2025-7786: Gnuboard g6 · Cross-site Scripting

Affects Gnuboard g6Source CVE Database V5

Public exploit available · CVSS 5.1 Medium.

Data as of 26 Oct 2026, 10:12 UTC

CVSS 4.0 base score

5.1Medium

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 20% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P

Base metrics

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: Passive
Vulnerable system confidentiality: None
Vulnerable system integrity: Low
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Threat metrics

Exploit Maturity: POC

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

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, 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: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: Passive: Successful exploitation of this vulnerability requires limited interaction by the targeted user with the vulnerable system and the attacker’s payload. These interactions would be considered involuntary and do not require that the user actively subvert protections built into the vulnerable system.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system 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 to the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.
Exploit Maturity: POC: Based on threat intelligence sources each of the following must apply: · Proof-of-concept is publicly available · No knowledge of reported attempts to exploit this vulnerability · No knowledge of publicly available solutions used to simplify attempts to exploit the vulnerability

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 18 Jul 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: evidence found.
CVSS exploit maturity: proof of concept public
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), CVSS vector, the Metasploit, Exploit-DB and nuclei-templates index as of 26 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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
GitHubgnuboard/g6`pkg:github/gnuboard/g6`Other threats	Affected 6.0.0 – 6.0.10 11 affected builds	Fixed in–

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

AI-suggested

Immediate mitigation should include implementing Web Application Firewall (WAF) rules to detect and block malicious payloads targeting the /bbs/scrap_popin_update/qa/ endpoint.
Apply strict Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers.
Sanitize and validate all user inputs on the server side, especially those processed by the Post Reply Handler, to neutralize malicious code.
Monitor web server logs for unusual requests or payloads indicative of XSS attempts.
Limit user privileges to the minimum necessary to reduce the impact of compromised accounts.
Educate users about the risks of clicking unknown links and encourage reporting suspicious activity.
Stay alert for official patches or updates from the Gnuboard project and apply them promptly once available.
Consider temporary disabling or restricting access to the vulnerable endpoint if feasible until a patch is released.
Conduct regular security assessments and penetration tests focusing on web application input validation.

Description

A vulnerability, which was classified as problematic, has been found in Gnuboard g6 up to 6.0.10. This issue affects some unknown processing of the file /bbs/scrap_popin_update/qa/ of the component Post Reply Handler. The manipulation leads to cross site scripting. The attack may be initiated remotely. The exploit has been disclosed to the public and may be used.

Impact

For European organizations using Gnuboard g6 for forums, community portals, or internal communication platforms, this XSS vulnerability poses a significant risk. Successful exploitation could lead to theft of session cookies, enabling attackers to impersonate legitimate users, including administrators. This could result in unauthorized actions, data manipulation, or further compromise of internal systems. The injected scripts could also be used to deliver malware or redirect users to malicious sites, impacting user trust and organizational reputation. Given the remote exploitability and lack of required privileges, attackers could target a wide range of users, including employees and customers. The medium severity score reflects moderate impact, but the potential for chained attacks (e.g., leveraging XSS to escalate privileges or conduct social engineering) increases the threat level. European organizations in sectors such as education, government, and SMEs that rely on Gnuboard for community engagement are particularly vulnerable. Additionally, the public disclosure without available patches heightens the urgency for mitigation to prevent exploitation.

References

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