# CVE-2026-101900: Axios: Fetch Adapter Header Injection via Inherited FormData getHeaders

> Prototype pollution allows attackers to inject malicious headers into Axios fetch requests, potentially bypassing security controls or altering request behavior.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:H/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Sep 2026
- **Updated:** 28 Sep 2026
- **Also known as:** CLEANSTART-2026-AM75023, CLEANSTART-2026-MF48068, CLEANSTART-2026-RK00164, DEBIAN-CVE-2026-101900, ECHO-6b1e-ec03-9a56, GHSA-4hqw-qxg8-jxx2, MINI-24m8-2php-hcfr, MINI-2h3g-6cxx-jjp9, MINI-5jff-mwpw-455v, MINI-c857-rhm8-vp67, MINI-cpv4-6582-5r6q, MINI-cqfp-9hwj-4g8m, MINI-crm2-33jg-qg2v, MINI-g3wf-4xxg-hx54, MINI-m3mp-5g98-346h, MINI-prc3-wp43-r87m, MINI-rw5f-7c99-wx2f, MINI-v8xw-2pp7-355q, MINI-vf7q-8gw7-p2qg, MINI-xrhv-vh7h-g9rv, MINI-xw27-jc36-rv23, UBUNTU-CVE-2026-101900

## What is CVE-2026-101900?

CVE-2026-101900 is a medium-severity code injection vulnerability in axios, published on 28 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Axios is a promise-based HTTP client for the browser and Node.js. From 1.12.0 until 1.20.0, ResolveConfig reads inherited Symbol.toStringTag, append, and getHeaders properties while resolving FormData headers. A separate same-process prototype-pollution flaw supplies an array or non-plain class instance whose inherited properties make it appear FormData-like; plain objects are blocked. The inherited getHeaders function can return attacker-controlled headers that resolveConfig merges into a fetch adapter request. Attacker-controlled headers can alter authorization, cache, metadata-service, or application-specific request behavior. This issue is fixed in version 1.20.0.

Weakness: CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component), CWE-693 (Protection Mechanism Failure), CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes)

## Which versions are affected by CVE-2026-101900?

2 open source packages ship an affected version, including axios.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `axios` | npm | From 1.12.0 | 1.20.0 |
| `axios` | npm | From 1.12.0 | 1.20.0 |

## How do I fix CVE-2026-101900?

Upgrade axios to 1.20.0 or later.

## Is CVE-2026-101900 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-101900 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-101900 and fix it if it is affected.

What it is: CVE-2026-101900 is a medium-severity code injection vulnerability in axios, published on 28 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-101900 exists.

Affected packages and fixed versions:
- axios (npm): affected from 1.12.0; fixed in 1.20.0
- axios (npm): affected from 1.12.0; fixed in 1.20.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-101900/ (Markdown: https://insights.sbomify.com/CVE-2026-101900/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-101900
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-101900
- OSV: https://osv.dev/vulnerability/CVE-2026-101900

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-101900/
Summaries are generated and may contain mistakes; the official description above is the record.