CVE-2026-112374VulnerabilityPublished 30 Oct 2026

FOSSBilling before 0.8.9 contains a Cross-Site Request Forgery vulnerability in the staff guest login endpoint (POST

Source GCVE Database

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Authoritative record:CVE-2026-112374· Medium 5.1

Not known to be exploited · CVSS 5.1 Medium : upgrade to 0.8.9 when convenient.

Data as of 30 Oct 2026, 17:05 UTC

CVSS 4.0 base score

5.1Medium

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

Thin evidence

One scorer or none

CVSS scores by source
CNA (VulnCheck)	CVSS 4.0	5.1
CNA (VulnCheck)	CVSS 3.1	4.3

Patch: Available – fixed in 0.8.9

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

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

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.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 30 Oct 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.

ghsa-595p-xmhc-mfxv

What to do

Upgrade FOSSBilling to 0.8.9.

Affected software

Product	Affected	Fixed in
FOSSBillingFOSSBilling	Affected >=0.1.0 <0.8.9	Fixed in 0.8.9
GitHubFOSSBilling`pkg:github/FOSSBilling`Other threats	Affected >=0.1.0 <0.8.9	Fixed in 0.8.9

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

AI-suggested

Upgrade FOSSBilling to version 0.8.9 or later where this CSRF vulnerability is fixed. Since the vulnerability is addressed in 0.8.9, applying this official fix will mitigate the issue. No other specific mitigations are indicated.

Description

FOSSBilling versions before 0.8.9 have a Cross-Site Request Forgery (CSRF) vulnerability in the staff guest login endpoint. This flaw allows remote attackers to force authentication by exploiting missing CSRF or Origin validation on the staff_login action. An attacker can craft an auto-submitting HTML form with attacker-controlled credentials to silently log a victim's browser into the attacker's staff account.

Impact

An attacker can remotely force a victim's browser to authenticate as the attacker's staff account without the victim's consent. This could allow unauthorized access to staff-level functionality in FOSSBilling, potentially leading to unauthorized actions performed with staff privileges. The CVSS score of 4.3 indicates a medium severity impact with low complexity and no direct confidentiality or availability impact, but with integrity impact limited to forced authentication.

Summary

The vulnerability in FOSSBilling prior to version 0.8.9 exists in the POST /api/guest/staff/login endpoint. The function checkGuestClientAuthentication() only allowlists client_login and client_create for CSRF protection, but omits staff_login. This omission means that staff_login requests lack CSRF or Origin header validation, enabling attackers to perform a CSRF attack that forces a victim's browser to authenticate as the attacker’s staff account via an auto-submitting HTML form.

CWE-352Cross-Site Request Forgery (opens in a new tab)
Compound weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #3OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.
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
Ensure that the application is free of cross-site scripting issues (CWE-79), because most CSRF defenses can be bypassed using attacker-controlled script.
Architecture and Design
Generate a unique nonce for each form, place the nonce into the form, and verify the nonce upon receipt of the form. Be sure that the nonce is not predictable (CWE-330).
OWASP Cheat Sheets
REST Assessment (opens in a new tab)
REST Security (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
Authorization Testing Automation (opens in a new tab)
Insecure Direct Object Reference Prevention (opens in a new tab)
OWASP ASVS 4.0.3
V13.2.3 (opens in a new tab)
V4.2.2 (opens in a new tab)
V13.3.2 (opens in a new tab)
Attack patterns
JSON Hijacking (aka JavaScript Hijacking) (opens in a new tab)
Cross-Domain Search Timing (opens in a new tab)
Cross Site Identification (opens in a new tab)
Cross Site Request Forgery (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 30 Oct 2026, 17:05 UTC

WeaknessesCWE-352

Technical details

References

Community reviews

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