| Package | Affected versions | Patched versions |
|---|---|---|
| axios | ≥ 1.0.0, < 1.16.0< 0.32.0 | 1.16.00.32.0 |
| axios | ≥ 1.0.0, < 1.16.0< 0.32.0 | 1.16.00.32.0 |
axios 1.15.2 exposes two read-side prototype-pollution gadgets. When Object.prototype is polluted by an upstream dependency in the same process (e.g. lodash _.merge / CVE-2018-16487), axios silently picks up the polluted values:
lib/utils.js line 406 builds merge()'s accumulator as result = {}, so result[targetKey] (line 414) walks Object.prototype and the polluted bucket's own keys are copied into the merged headers and ride out on the wire.lib/core/mergeConfig.js line 26 builds the hasOwnProperty descriptor as a plain-object literal. Object.defineProperty reads descriptor.get/descriptor.set via the prototype chain, so a polluted Object.prototype.get or Object.prototype.set makes the call throw TypeError synchronously on every axios request.| Polluted slot | Effect |
|---|---|
Object.prototype.common | injects headers on every method |
Object.prototype.delete / .head / .post / .put / .patch / .query | injects headers on the matching method |
Object.prototype.get | every axios request throws TypeError: Getter must be a function from mergeConfig.js:26 |
Object.prototype.set | every axios request throws TypeError: Setter must be a function from mergeConfig.js:26 |
Per-request headers (axios.request(url, { headers: {...} })) overwrite polluted entries. Polluting Object.prototype.get triggers the crash before any header is built.
const axios = require('axios');
// Finding A - header injection
Object.prototype.common = { 'X-Poisoned': 'yes' };
await axios.get('http://api.example.com/users');
// Wire request carries `X-Poisoned: yes`.
// Finding B - crash DoS
Object.prototype.get = { something: 'anything' };
await axios.get('http://api.example.com/users');
// TypeError: Getter must be a function: #<Object>
// at Function.defineProperty (<anonymous>)
// at mergeConfig (lib/core/mergeConfig.js:26:10)
Running one of these products? Scan your site to see whether it exposes a vulnerable version.
Scan my site freeContent-Length: 99999): receiver waits for a body that never arrives. Affects requests with a body.Transfer-Encoding: chunked rides alongside axios's auto Content-Length): receiver rejects with 400 Bad Request. Affects requests with a body.If-None-Match: *): receiver returns empty 304 Not Modified. Affects GET / HEAD.Object.prototype.get / .set): every axios request fails synchronously with TypeError, not AxiosError, so handlers filtering on error.isAxiosError mishandle the failure.flowchart TD
ROOT["Polluted Object.prototype<br/>via upstream gadget (e.g. lodash <= 4.17.10 _.merge / CVE-2018-16487)<br/>axios <= 1.15.2"]
ROOT --> CLASS_A["A. Arbitrary HTTP Header Injection<br/>Polluted defaults.headers slot rides along on every outbound axios request"]
ROOT --> CLASS_B["B. Crash DoS via Object.prototype.get / .set<br/>Polluted descriptor breaks Object.defineProperty in mergeConfig"]
CLASS_A --> PRE_A["Precondition: header not set per-request by the app<br/>Injected via defaults.headers slot<br/>(common, delete, head, post, put, patch, query)"]
PRE_A --> PA1["Response Suppression<br/>Trigger: common = {If-None-Match: *}<br/>Affects GET / HEAD"]
PA1 --> SA1["DoS<br/>304 Not Modified empty"]
PRE_A --> PA2["Server Hang<br/>Trigger: common = {Content-Length: 99999}<br/>Affects requests with body"]
PA2 --> SA2["DoS<br/>connection hang"]
PRE_A --> PA3["CL+TE Conflict<br/>Trigger: common = {Transfer-Encoding: chunked}<br/>Affects requests with body"]
PA3 --> SA3["DoS<br/>400 Bad Request"]
CLASS_B --> SB1["DoS<br/>TypeError: Getter / Setter must be a function<br/>Crashes every axios request, not only GET"]
%% Styles
style ROOT fill:#f87171,stroke:#991b1b,color:#fff
style CLASS_A fill:#fb923c,stroke:#9a3412,color:#fff
style CLASS_B fill:#fb923c,stroke:#9a3412,color:#fff
style PRE_A fill:#e2e8f0,stroke:#64748b,color:#1e293b
style PA1 fill:#fbbf24,stroke:#92400e,color:#000
style PA2 fill:#fbbf24,stroke:#92400e,color:#000
style PA3 fill:#fbbf24,stroke:#92400e,color:#000
style SA1 fill:#ef4444,stroke:#991b1b,color:#fff
style SA2 fill:#ef4444,stroke:#991b1b,color:#fff
style SA3 fill:#ef4444,stroke:#991b1b,color:#fff
style SB1 fill:#ef4444,stroke:#991b1b,color:#fff
Finding A. lib/utils.js:404-429's merge() creates result = {} at line 406. The dangerous-keys filter on lines 408-411 blocks the write side, but the read at line 414 (isPlainObject(result[targetKey])) still walks the prototype chain. When targetKey matches a polluted slot, result[targetKey] returns the polluted nested object, and the recursive merge(result[targetKey], val) on line 415 iterates that object's own keys via forEach and copies them as own properties into the new accumulator. Those keys flow through mergeConfig.js:35 → Axios.js:148 (utils.merge(headers.common, headers[config.method])) → Axios.js:155 (AxiosHeaders.concat(...)) → onto the wire via http.js:677 (headers: headers.toJSON()) → http.js:767 (transport.request(options, ...)).
Finding B. lib/core/mergeConfig.js:25 correctly makes config = Object.create(null), but the descriptor passed on line 26 is a plain-object literal - its get/set lookups walk Object.prototype. A polluted non-function Object.prototype.get or .set makes Object.defineProperty throw TypeError: Getter must be a function (or Setter must be a function) before the call returns. The descriptor is built unconditionally on every mergeConfig invocation, so every axios request throws - POST, PUT, DELETE, PATCH, HEAD, QUERY, not only GET.
Use null-prototype objects in place of the plain-object literals at lib/utils.js:406 and lib/core/mergeConfig.js:26-31. The same descriptor pattern recurs at lib/core/AxiosError.js:37, lib/core/AxiosHeaders.js:100, lib/utils.js:447/454/492/498, and lib/adapters/adapters.js:28/32.
lodash.merge prototype pollution in lodash <= 4.17.10