CVE-2025-27209VulnerabilityPublished 18 Jul 2025Updated 4 Nov 2025

CVE-2025-27209: nodejs node · CWE-407

Affects nodejs nodeSource CVE Database V5

Not known to be exploited · CVSS 7.5 High.

Data as of 26 Oct 2026, 08:30 UTC

CVSS 3.0 base score

7.5High

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

EPSS: 1.2% chance of exploitation in 30 days – higher than 69% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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

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: 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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 18 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 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 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
npmnode`pkg:npm/node`Other threats	Affected =24.0.0	Fixed in–

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AI-suggested

1. Upgrade Node.js: Monitor official Node.js releases and promptly upgrade to a patched version that addresses the HashDoS vulnerability once available. 2. Input Validation: Implement strict input validation and sanitization on all user-controlled strings that are processed or hashed to reduce the likelihood of crafted collision inputs. 3. Rate Limiting: Deploy rate limiting and throttling mechanisms on APIs and services to limit the number of requests from a single source, mitigating the impact of collision-based DoS attempts. 4. Monitoring and Alerting: Enhance monitoring for unusual CPU usage patterns and request anomalies that may indicate hash collision attacks. 5. Use Alternative Hashing: Where feasible, configure or patch applications to use more collision-resistant hashing algorithms or libraries. 6. Isolate Critical Services: Architect services to isolate Node.js components handling untrusted input, minimizing the blast radius of potential attacks. 7. Engage with Vendors: Coordinate with third-party vendors and cloud providers to ensure they are aware of the vulnerability and have applied necessary patches or mitigations.

Description

The V8 release used in Node.js v24.0.0 has changed how string hashes are computed using rapidhash. This implementation re-introduces the HashDoS vulnerability as an attacker who can control the strings to be hashed can generate many hash collisions - an attacker can generate collisions even without knowing the hash-seed. * This vulnerability affects Node.js v24.x users.

Impact

For European organizations, the primary impact of CVE-2025-27209 is the risk of denial of service attacks against Node.js applications running version 24.0.0. This can lead to service outages, degraded performance, and potential loss of availability for critical web services, APIs, or backend systems. Industries relying heavily on Node.js for real-time applications, e-commerce platforms, or cloud services could experience operational disruptions. The vulnerability does not compromise confidentiality or integrity directly but can indirectly affect business continuity and user trust. Given the ease of exploitation without authentication, attackers can launch large-scale or targeted DoS campaigns remotely. Organizations in sectors such as finance, telecommunications, and government services, which often deploy Node.js-based solutions, may face increased risk. Additionally, the lack of known exploits in the wild suggests a window for proactive mitigation before widespread attacks occur.

Summary

CVE-2025-27209 is a vulnerability identified in Node.js version 24.0.0 stemming from a change in the V8 JavaScript engine's string hashing mechanism. The V8 engine switched to using rapidhash for computing string hashes, which inadvertently reintroduced a HashDoS vulnerability (CWE-407). HashDoS attacks exploit the hash function's susceptibility to collisions, where an attacker crafts numerous input strings that hash to the same value. This causes hash table operations, such as lookups or insertions, to degrade from average O(1) time complexity to O(n), leading to significant CPU resource exhaustion. Notably, the attacker does not need knowledge of the hash seed, simplifying exploitation. The vulnerability affects Node.js 24.x users, specifically version 24.0.0, and can be triggered remotely without authentication or user interaction, as it relies on attacker-controlled input strings processed by the Node.js runtime. The CVSS v3.0 score of 7.5 reflects a high severity due to the network attack vector, low attack complexity, and the potential for complete denial of service (availability impact). No patches or exploits are currently documented, but the risk is substantial given Node.js's widespread use in web applications and services. The vulnerability's root cause is a regression in the V8 engine's hashing algorithm, emphasizing the importance of thorough testing when modifying fundamental components like hash functions.

CWE-407Inefficient Algorithmic Complexity (opens in a new tab)
Class weaknessLikelihood of exploit: Low
An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Nov 2025, 21:44 UTC

WeaknessesCWE-407

Technical details

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