VulnerabilityPublished 9 Feb 2026Updated 8 May 2026

CVE-2026-25639: Axios is Vulnerable to Denial of Service via proto Key in mergeConfig

Affects axiosSource GCVE Database

Not known to be exploited · CVSS 7.5 High : upgrade to 1.13.5 soon.

Data as of 27 Oct 2026, 00:07 UTC

CVSS 3.1 base score

7.5High

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

Patch: Available – fixed in 1.13.5, 0.30.3

CVSS:3.1/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 9 Feb 2026
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 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

Upgrade axios to 1.13.5; axios to 0.30.3.

Affected software

Product	Affected	Fixed in
npmaxios	Affected >=1.0.0 <1.13.5	Fixed in 1.13.5
npmaxios	Affected <0.30.3	Fixed in 0.30.3

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

Description

# Denial of Service via **proto** Key in mergeConfig ### Summary The `mergeConfig` function in axios crashes with a TypeError when processing configuration objects containing `__proto__` as an own property. An attacker can trigger this by providing a malicious configuration object created via `JSON.parse()`, causing complete denial of service. ### Details The vulnerability exists in `lib/core/mergeConfig.js` at lines 98-101: ```javascript utils.forEach(Object.keys({ ...config1, ...config2 }), function computeConfigValue(prop) { const merge = mergeMap[prop] || mergeDeepProperties; const configValue = merge(config1[prop], config2[prop], prop); (utils.isUndefined(configValue) && merge !== mergeDirectKeys) || (config[prop] = configValue); }); ``` When `prop` is `'__proto__'`: 1. `JSON.parse('{"__proto__": {...}}')` creates an object with `__proto__` as an own enumerable property 2. `Object.keys()` includes `'__proto__'` in the iteration 3. `mergeMap['__proto__']` performs prototype chain lookup, returning `Object.prototype` (truthy object) 4. The expression `mergeMap[prop] || mergeDeepProperties` evaluates to `Object.prototype` 5. `Object.prototype(...)` throws `TypeError: merge is not a function` The `mergeConfig` function is called by: - `Axios._request()` at `lib/core/Axios.js:75` - `Axios.getUri()` at `lib/core/Axios.js:201` - All HTTP method shortcuts (`get`, `post`, etc.) at `lib/core/Axios.js:211,224` ### PoC ```javascript import axios from "axios"; const maliciousConfig = JSON.parse('{"__proto__": {"x": 1}}'); await axios.get("https://httpbin.org/get", maliciousConfig); ``` **Reproduction steps:** 1. Clone axios repository or `npm install axios` 2. Create file `poc.mjs` with the code above 3. Run: `node poc.mjs` 4. Observe the TypeError crash **Verified output (axios 1.13.4):** ``` TypeError: merge is not a function at computeConfigValue (lib/core/mergeConfig.js:100:25) at Object.forEach (lib/utils.js:280:10) at mergeConfig (lib/core/mergeConfig.js:98:9) ``` **Control tests performed:** | Test | Config | Result | |------|--------|--------| | Normal config | `{"timeout": 5000}` | SUCCESS | | Malicious config | `JSON.parse('{"__proto__": {"x": 1}}')` | **CRASH** | | Nested object | `{"headers": {"X-Test": "value"}}` | SUCCESS | **Attack scenario:** An application that accepts user input, parses it with `JSON.parse()`, and passes it to axios configuration will crash when receiving the payload `{"__proto__": {"x": 1}}`. ### Impact **Denial of Service** - Any application using axios that processes user-controlled JSON and passes it to axios configuration methods is vulnerable. The application will crash when processing the malicious payload. Affected environments: - Node.js servers using axios for HTTP requests - Any backend that passes parsed JSON to axios configuration This is NOT prototype pollution - the application crashes before any assignment occurs.

CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (opens in a new tab)
Variant weakness
The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.
Implementation
By freezing the object prototype first (for example, Object.freeze(Object.prototype)), modification of the prototype becomes impossible.
Architecture and Design
By blocking modifications of attributes that resolve to object prototype, such as proto or prototype, this weakness can be mitigated.
Implementation · Input Validation
When handling untrusted objects, validating using a schema can be used.
OWASP Cheat Sheets
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V5.1.2 (opens in a new tab)
Attack patterns
Accessing Functionality Not Properly Constrained by ACLs (opens in a new tab)
Exploiting Incorrectly Configured Access Control Security Levels (opens in a new tab)
Manipulating User-Controlled Variables (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-754Improper Check for Unusual or Exceptional Conditions (opens in a new tab)
Class weaknessLikelihood of exploit: MediumOWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product.
Requirements · Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation
Check the results of all functions that return a value and verify that the value is expected.
Implementation
If using exception handling, catch and throw specific exceptions instead of overly-general exceptions (CWE-396, CWE-397). Catch and handle exceptions as locally as possible so that exceptions do not propagate too far up the call stack (CWE-705). Avoid unchecked or uncaught exceptions where feasible (CWE-248).
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.7 (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

WeaknessesCWE-1321, CWE-754

Technical details

References

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