VulnerabilityPublished 19 Feb 2026Updated 23 Feb 2026

CVE-2026-2709: busy · Open Redirect

Affects busySource 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 22% 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 19 Feb 2026
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
busy	Affected 2.5.0 – 2.5.5 6 affected builds	Fixed in–

AI-suggested

Implement strict validation and sanitization of the 'state' parameter in the Callback Handler to ensure it only allows safe, expected URLs or relative paths.
Employ allowlists for redirect URLs to prevent arbitrary external redirects.
Use security headers such as Content Security Policy (CSP) and X-Frame-Options to mitigate the impact of redirection-based attacks.
Educate users to recognize suspicious URLs and avoid clicking unknown links.
Monitor web server logs for unusual redirect patterns or spikes in redirect-related errors.
If possible, upgrade to a patched version once available or apply custom patches to fix the validation logic.
Consider implementing multi-factor authentication to reduce the risk of session hijacking following phishing.
Use web application firewalls (WAFs) to detect and block exploit attempts targeting this vulnerability.
Engage with the busy project maintainers or community to encourage timely patch release.

Description

A flaw has been found in busy up to 2.5.5. The affected element is an unknown function of the file source-code/busy-master/src/server/app.js of the component Callback Handler. Executing a manipulation of the argument state can lead to open redirect. It is possible to launch the attack remotely. The exploit has been published and may be used. The project was informed of the problem early through an issue report but has not responded yet.

Impact

The primary impact of this vulnerability is the potential for attackers to conduct phishing attacks by redirecting users to malicious websites that may steal credentials, deliver malware, or perform other social engineering attacks. While the vulnerability does not directly compromise system confidentiality, integrity, or availability, it undermines user trust and can serve as a stepping stone for more severe attacks such as session hijacking or credential theft. Organizations relying on busy for web services may face reputational damage and increased risk of user-targeted attacks. Since exploitation requires user interaction, the scope is somewhat limited but still significant, especially in environments with high user traffic or where users are less security-aware. The absence of an official patch increases the window of exposure. Attackers could leverage this vulnerability in targeted campaigns or broad phishing attempts, potentially affecting a wide user base.

Summary

CVE-2026-2709 identifies an open redirect vulnerability in the busy project, affecting versions 2.5.0 through 2.5.5. The vulnerability exists in an unknown function within the Callback Handler component located in source-code/busy-master/src/server/app.js. The root cause is insufficient validation or sanitization of the 'state' parameter, which can be manipulated by an attacker to redirect users to arbitrary external URLs. This type of vulnerability is commonly exploited in phishing attacks, where users are tricked into clicking malicious links that appear legitimate but redirect to harmful sites. The vulnerability is remotely exploitable without requiring authentication, but it does require user interaction to trigger the redirect. The CVSS 4.0 vector indicates network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:L), user interaction required (UI:P), and limited impact on confidentiality and integrity, with no impact on availability. The project was notified early but has not yet responded or issued a patch. Public exploits exist, increasing the risk of exploitation in the wild. The lack of a patch and the presence of a public exploit necessitate immediate attention from users of the affected versions.

References

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