CVE-2025-62595VulnerabilityPublished 21 Oct 2025

CVE-2025-62595: koajs koa · Open Redirect

Affects koajs koaSource CVE Database V5

Mentioned vulnerabilities

CVE-2025-8129

Not known to be exploited · CVSS 4.3 Medium : upgrade to 3.0.3 or 2.16.3 when convenient.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

4.3Medium

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 21% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.0.3, 2.16.3

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Unchanged
Confidentiality: None
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: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
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: None: There is no loss of confidentiality within 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 21 Oct 2025
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

Upgrade koajs koa to 3.0.3 or 2.16.3.

Affected software

Product	Affected	Fixed in
npmkoa`pkg:npm/koa`Other threats	Affected >=2.16.2 <2.16.3 >=3.0.1 <3.0.3	Fixed in 2.16.3 3.0.3

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

AI-suggested

European organizations should take the following specific mitigation steps: 1) Immediately upgrade all Koa.js dependencies to version 3.0.3 or later, where the vulnerability is patched. 2) Audit all web applications using Koa to identify affected versions and confirm no legacy deployments remain. 3) Implement strict input validation and sanitization on any user-controllable redirect URLs beyond relying on framework defaults. 4) Employ Content Security Policy (CSP) headers to restrict navigation to trusted domains, reducing the impact of open redirects. 5) Use anti-phishing training and awareness programs to educate users about suspicious links and redirects. 6) Monitor web application logs for unusual redirect patterns or Referer header anomalies that may indicate exploitation attempts. 7) Consider implementing multi-factor authentication (MFA) to reduce the impact of credential theft resulting from phishing. 8) Engage in regular dependency management and vulnerability scanning to detect and remediate similar issues proactively. These steps go beyond generic advice by focusing on both patching and layered defenses against redirect-based phishing attacks.

Description

Koa is expressive middleware for Node.js using ES2017 async functions. In versions 2.16.2 to before 2.16.3 and 3.0.1 to before 3.0.3, a bypass to CVE-2025-8129 was discovered in the Koa.js framework affecting its back redirect functionality. In certain circumstances, an attacker can manipulate the Referer header to force a user’s browser to navigate to an external, potentially malicious website. This occurs because the implementation incorrectly treats some specially crafted URLs as safe relative paths. Exploiting this vulnerability could allow attackers to perform phishing, social engineering, or other redirect-based attacks on users of affected applications. This issue has been patched in version 3.0.3.

Impact

For European organizations, the primary impact of CVE-2025-62595 lies in the increased risk of successful phishing and social engineering attacks facilitated by malicious redirects. Organizations that use Koa.js in their web applications, especially those handling sensitive user data or providing critical services, may see increased exposure to credential theft, session hijacking, or malware delivery through redirected malicious sites. While the vulnerability does not directly compromise system confidentiality or availability, the indirect consequences of successful phishing can lead to data breaches, financial loss, reputational damage, and regulatory penalties under GDPR if personal data is compromised. The medium severity rating reflects that the vulnerability is exploitable remotely without authentication but requires user interaction, limiting automated exploitation. Nonetheless, the widespread use of Node.js and Koa.js in European startups, SMEs, and enterprise web applications means that the threat surface is significant. Organizations in sectors such as finance, healthcare, and e-commerce are particularly sensitive to phishing risks and should prioritize patching. Additionally, regulatory scrutiny in Europe on data protection and user safety increases the importance of mitigating such vulnerabilities promptly.

CWE-601URL Redirection to Untrusted Site ('Open Redirect') (opens in a new tab)
Base weaknessLikelihood of exploit: LowOWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Architecture and Design
Use an intermediate disclaimer page that provides the user with a clear warning that they are leaving the current site. Implement a long timeout before the redirect occurs, or force the user to click on the link. Be careful to avoid XSS problems (CWE-79) when generating the disclaimer page.
Architecture and Design · Enforcement by Conversion
When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
OWASP Cheat Sheets
Mass Assignment (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V5.1.5 (opens in a new tab)
Attack patterns
Cross-Site Flashing (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 21 Oct 2025, 16:28 UTC

WeaknessesCWE-601

Technical details

References

Community reviews

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