CVE-2026-42034 — axios
MEDIUMCVE-2026-42034 is a medium-severity (CVSS 5.3) CWE-770 vulnerability in axios. A fix is available for axios — see the affected versions and patch details below.
Axios: HTTP adapter streamed uploads bypass maxBodyLength when maxRedirects: 0
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42034.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-42034 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
axiosnpmDescription
Summary
For stream request bodies, maxBodyLength is bypassed when maxRedirects is set to 0 (native http/https transport path). Oversized streamed uploads are sent fully even when the caller sets strict body limits.
Details
Relevant flow in lib/adapters/http.js:
- 556-564: maxBodyLength check applies only to buffered/non-stream data.
- 681-682: maxRedirects === 0 selects native http/https transport.
- 694-699: options.maxBodyLength is set, but native transport does not enforce it.
- 925-945: stream is piped directly to socket (data.pipe(req)) with no Axios byte counting.
This creates a path-specific bypass for streamed uploads.
PoC
Environment:
- Axios main at commit f7a4ee2
- Node v24.2.0
Steps:
- Start an HTTP server that counts uploaded bytes and returns {received}.
- Send a 2 MiB Readable stream with:
- adapter: 'http'
- maxBodyLength: 1024
- maxRedirects: 0
Observed:
- Request succeeds; server reports received: 2097152.
Control checks:
- Same stream with default/nonzero redirects: rejected with ERR_FR_MAX_BODY_LENGTH_EXCEEDED.
- Buffered body with maxRedirects: 0: rejected with ERR_BAD_REQUEST.
Impact
Type: DoS / uncontrolled upstream upload / resource exhaustion. Impacted: Node.js services using streamed request bodies with maxBodyLength expecting hard enforcement, especially when following Axios guidance to use maxRedirects: 0 for streams.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | axios | ≥ 1.0.0&&< 1.15.1 | 1.15.1npm install axios@1.15.1 |
| 📦npm | axios | all versions | 0.31.1npm install axios@0.31.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for axios, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update axios to 1.15.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42034 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-42034 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-42034. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-42034 in your dependencies?
O3 Security finds CVE-2026-42034 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.