CVE-2021-38384: Serverless Offline 8.0.0 returns a 403 HTTP status code for a route that has a trailing / character, which mig

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CRITICAL 9.8REMOTEDOWNGRADE

CVE-2021-38384 is a critical-severity flaw (CVSS 9.8) affecting serverless offline. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Serverless Offline 8.0.0 returns a 403 HTTP status code for a route that has a trailing / character, which might cause a developer to implement incorrect access control, because the actual behavior within the Amazon AWS environment is a 200 HTTP status code (i.e., possibly greater than expected permissions).

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

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

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.5% (top 26%)
CISA exploited list	No
Weakness	CWE-755
Published	2021-08-10
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: serverless offline project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-08-10 18:15 UTCPublished CVE record published
2026-06-17 04:01 UTCUpdated Record last modified

serverless offline project serverless offline DOWNGRADE

Affected: 8.0.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0.0

1. Check installed version

apt-cache policy serverless-offline || rpm -q serverless-offline || serverless-offline --version

2. No fixed release: DOWNGRADE to a release before 8.0.0 (Debian / Ubuntu)

apt-cache madison serverless-offline sudo apt install serverless-offline=<VERSION_BEFORE_8.0.0> sudo apt-mark hold serverless-offline

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list serverless-offline sudo dnf downgrade serverless-offline-<VERSION_BEFORE_8.0.0> sudo dnf versionlock add serverless-offline

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-2021-38384?

serverless offline: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-38384 being exploited?

CVE-2021-38384 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-2021-38384 affect?

CVE-2021-38384 affects serverless offline. Severity is critical (CVSS 9.8). Serverless Offline 8.0.0 returns a 403 HTTP status code for a route that has a trailing / character, which might cause a developer to implement incorrect access control, because the actual behavior within the Amazon AWS environment is a 200

How urgent is CVE-2021-38384?

Priority 63/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

AWS vulnerabilities

References

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