CVE-2025-7339VulnerabilityPublished 17 Jul 2025

CVE-2025-7339: jshttp on-headers · CWE-241

Affects jshttp on-headersSource CVE Database V5

Not known to be exploited · CVSS 3.4 Low : upgrade to 1.1.0 when convenient.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

3.4Low

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 10% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.1.0

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

Attack Vector: Local
Attack Complexity: Low
Privileges Required: High
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: None

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

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: High: The attacker is authorized with (i.e., requires) privileges that provide significant (e.g., administrative) control over the vulnerable component that could affect component-wide settings and files.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
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 17 Jul 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 2026-10-26.

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 jshttp on-headers to 1.1.0.

Affected software

Product	Affected	Fixed in
npmon-headers`pkg:npm/on-headers`Other threats	Affected <1.1.0	Fixed in 1.1.0

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

AI-suggested

To mitigate CVE-2025-7339, European organizations should take the following specific actions: 1) Audit all Node.js applications and services to identify usage of the on-headers middleware, especially versions prior to 1.1.0. 2) Upgrade on-headers to version 1.1.0 or later, which contains the patch addressing this vulnerability. 3) Review application code to ensure that response.writeHead() is never called with an array argument; refactor code to always use an object for headers. 4) Implement automated code scanning or static analysis tools to detect improper usage patterns of response.writeHead() and middleware versions. 5) Conduct thorough testing of HTTP response headers after upgrades or code changes to verify that headers are correctly set and no unintended modifications occur. 6) Enforce strict access controls and monitoring on systems with privileged accounts to reduce the risk of exploitation requiring high privileges. 7) Incorporate this vulnerability into the organization's vulnerability management and patching processes to ensure timely updates. These steps go beyond generic advice by focusing on code-level review, automated detection, and privileged access management tailored to this specific vulnerability.

Description

on-headers is a node.js middleware for listening to when a response writes headers. A bug in on-headers versions `<1.1.0` may result in response headers being inadvertently modified when an array is passed to `response.writeHead()`. Users should upgrade to version 1.1.0 to receive a patch. Uses are strongly encouraged to upgrade to `1.1.0`, but this issue can be worked around by passing an object to `response.writeHead()` rather than an array.

Impact

For European organizations, the impact of CVE-2025-7339 is generally low but not negligible. Many European enterprises and service providers rely on Node.js for backend services, including web applications and APIs. If these applications use the on-headers middleware and pass arrays to response.writeHead(), they risk unintended header modifications that could lead to security misconfigurations or functional issues. This could indirectly expose sensitive information or weaken security controls such as Content Security Policy (CSP), CORS headers, or authentication-related headers. While the vulnerability does not directly allow remote code execution or denial of service, the subtle integrity and confidentiality impacts could be exploited in complex attack chains or combined with other vulnerabilities. Organizations handling sensitive data, such as financial institutions, healthcare providers, or government services, should be particularly cautious. The requirement for high privileges to exploit reduces the risk from external attackers but raises concerns about insider threats or compromised privileged accounts. Overall, the threat is more relevant in environments where strict HTTP header control is critical for security compliance or data protection under regulations like GDPR.

CWE-241Improper Handling of Unexpected Data Type (opens in a new tab)
Base weakness
The product does not handle or incorrectly handles when a particular element is not the expected type, e.g. it expects a digit (0-9) but is provided with a letter (A-Z).
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.
Implementation · Input Validation
Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174).
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
OWASP ASVS 4.0.3
V1.5.1 (opens in a new tab)
Attack patterns
Passing Local Filenames to Functions That Expect a URL (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 17 Jul 2025, 16:16 UTC

WeaknessesCWE-241

Technical details

References

Community reviews

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