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Low, CVSS 3.7amended

Axios: Null Byte Injection via Reverse-Encoding in AxiosURLSearchParams

CVE-2026-42040GHSA-xhjh-pmcv-23jw

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (axios 1.15.1, 0.31.1), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • npm axios

    Affected
    >= 1.0.0, < 1.15.1<= 0.31.0
    Fixed in
    0.31.1, 1.15.1

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
3.7 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
EPSS
  • CVE-2026-42040: 0.22% estimated exploitation activity in the next 30 days; percentile 12.22 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Vulnerability Disclosure: Null Byte Injection via Reverse-Encoding in AxiosURLSearchParams Summary The encode() function in lib/helpers/AxiosURLSearchParams.js contains a character mapping (charMap) at line 21 that reverses the safe percent-encoding of null bytes. After encodeURIComponent('\x00') correctly produces the safe sequence %00, the charMap entry '%00': '\x00' converts it back to a raw null byte. This is a clear encoding defect: every other charMap entry encodes in the safe direction (literal → percent-encoded), while this single entry decodes in the opposite (dangerous) direction. Severity: Low (CVSS 3.7) Affected Versions: All versions containing this charMap entry Vulnerable Component: lib/helpers/AxiosURLSearchParams.js:21 CWE - CWE-626: Null Byte Interaction Error (Poison Null Byte) - CWE-116: Improper Encoding or Escaping of Output CVSS 3.1 Score: 3.7 (Low) Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N | Metric | Value | Justification | |---|---|---| | Attack…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-xhjh-pmcv-23jw

  2. Revision 1 · created ·

    Published from osv record GHSA-xhjh-pmcv-23jw

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-42040

Advisory: Axios: Null Byte Injection via Reverse-Encoding in AxiosURLSearchParams
IDs: CVE-2026-42040, GHSA-xhjh-pmcv-23jw
Record: https://patchnext.com/advisories/cve-2026-42040 (revision 2, source checked 26 Oct 2026, 12:51 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: axios 1.15.1, 0.31.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm axios: affected >= 1.0.0, < 1.15.1; <= 0.31.0; fixed in 0.31.1, 1.15.1

## Suggested inspection (read-only)
- `npm ls axios --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on axios.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-xhjh-pmcv-23jw (OSV record GHSA-xhjh-pmcv-23jw lists affected ranges: npm axios >=1.0.0 =0 <0.31.1 (fixed))
- Verified: https://github.com/advisories/GHSA-xhjh-pmcv-23jw (GitHub-reviewed advisory GHSA-xhjh-pmcv-23jw lists affected ranges: npm axios >=1.0.0 =0 <=0.31.0)

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