CVE-2026-18248: @fastify/aws-lambda version 6.4.0 decorates each Fastify request with request.awsLambda.event and request.awsL

Q: How do I fix CVE-2026-18248?

fastify\/aws-lambda: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2026-18248 being exploited?

CVE-2026-18248 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-18248 affect?

CVE-2026-18248 affects fastify\/aws-lambda. Severity is critical (CVSS 9.1). @fastify/aws-lambda version 6.4.0 decorates each Fastify request with request.awsLambda.event and request.awsLambda.context, values that applications are documented to use for authorization decisions such as reading API Gateway authorizer c

Q: How urgent is CVE-2026-18248?

Priority 50/100. Critical severity; Remotely exploitable, no login, no user action; On your watchlist

This month

CRITICAL 9.1REMOTEWATCHLISTDOWNGRADE

CVE-2026-18248 is a critical-severity flaw (CVSS 9.1) affecting fastify\/aws-lambda. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

@fastify/aws-lambda version 6.4.0 decorates each Fastify request with request.awsLambda.event and request.awsLambda.context, values that applications are documented to use for authorization decisions such as reading API Gateway authorizer claims. In the default configuration, the getter that populates this decoration reads the client-controlled x-apigateway-event and x-apigateway-context HTTP headers before falling back to the trusted internal re

Why this priority

Critical severity
Remotely exploitable, no login, no user action
On your watchlist

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 68%)
CISA exploited list	No
Weakness	CWE-345
Published	2026-08-03
Last modified	2026-09-04

Publisher (CNA): openjs · Vendor: fastify

Last updated 2026-09-04 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-03 16:16 UTCPublished CVE record published
2026-09-04 13:44 UTCUpdated Record last modified

fastify fastify\/aws-lambda DOWNGRADE

Affected: 6.4.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 6.4.0

1. Check installed version

npm ls fastifyaws-lambda

2. No fixed release: DOWNGRADE to a release before 6.4.0

npm view fastifyaws-lambda versions npm install fastifyaws-lambda@"<6.4.0"

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2026-18248?

fastify\/aws-lambda: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-18248 being exploited?

CVE-2026-18248 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-2026-18248 affect?

CVE-2026-18248 affects fastify\/aws-lambda. Severity is critical (CVSS 9.1). @fastify/aws-lambda version 6.4.0 decorates each Fastify request with request.awsLambda.event and request.awsLambda.context, values that applications are documented to use for authorization decisions such as reading API Gateway authorizer c

How urgent is CVE-2026-18248?

Priority 50/100. Critical severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

AWS vulnerabilities

References

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