CVE-2026-48713: Versions prior to 2.6.6 are vulnerable to prototype pollution via crafted missing-key strings when used to per

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CRITICAL 9.1REMOTEUPGRADE

CVE-2026-48713 is a critical-severity flaw (CVSS 9.1) affecting i18next-fs-backend. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Versions prior to 2.6.6 are vulnerable to prototype pollution via crafted missing-key strings when used to persist missing translation keys (e.g. via i18next-http-middleware's missingKeyHandler exposed to untrusted input). Backend.writeFile() splits each queued missing-key string on the configured keySeparator (default .) before calling the internal setPath() walker. The walker (getLastOfPath in lib/utils.js) did not guard against unsafe segments

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 57%)
CISA exploited list	No
Weakness	CWE-1321
Published	2026-06-15
Last modified	2026-10-25

Publisher (CNA): GitHub, Inc. · Vendor: i18next

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-15 22:16 UTCPublished CVE record published
2026-10-25 23:10 UTCUpdated Record last modified

i18next i18next-fs-backend UPGRADE

Affected: < 2.6.6

Fixed in: 2.6.6

Safe to downgrade to: no unaffected older release

1. Check installed version

npm ls i18next-fs-backend

2. UPGRADE to 2.6.6

npm install i18next-fs-backend@">=2.6.6"

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-48713?

i18next-fs-backend: upgrade to 2.6.6. Exact commands for each OS are on this page.

Is CVE-2026-48713 being exploited?

CVE-2026-48713 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-48713 affect?

CVE-2026-48713 affects i18next-fs-backend. Severity is critical (CVSS 9.1). Versions prior to 2.6.6 are vulnerable to prototype pollution via crafted missing-key strings when used to persist missing translation keys (e.g. via i18next-http-middleware's missingKeyHandler exposed to untrusted input). Backend.writeFile

How urgent is CVE-2026-48713?

Priority 48/100. Critical severity; Remotely exploitable, no login, no user action

References

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