CVE-2021-40663: deep.assign npm package 0.0.0-alpha.0 is vulnerable to Improperly Controlled Modification of Object Prototype

Q: How do I fix CVE-2021-40663?

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

Q: Is CVE-2021-40663 being exploited?

CVE-2021-40663 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-2021-40663 affect?

CVE-2021-40663 affects deep.assign. Severity is critical (CVSS 9.8). deep.assign npm package 0.0.0-alpha.0 is vulnerable to Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').

Q: How urgent is CVE-2021-40663?

Priority 64/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEDOWNGRADE

CVE-2021-40663 is a critical-severity flaw (CVSS 9.8) affecting deep.assign. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

deep.assign npm package 0.0.0-alpha.0 is vulnerable to Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').

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	1.8% (top 22%)
CISA exploited list	No
Weakness	CWE-1321
Published	2022-06-30
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: deep.assign project

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

Am I affected?

Timeline

2022-06-30 12:15 UTCPublished CVE record published
2026-06-17 04:07 UTCUpdated Record last modified

deep.assign project deep.assign DOWNGRADE

Affected: 0.0.0 alpha0

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.0.0

1. Check installed version

npm ls deep.assign

2. No fixed release: DOWNGRADE to a release before 0.0.0

npm view deep.assign versions npm install deep.assign@"<0.0.0"

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-2021-40663?

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

Is CVE-2021-40663 being exploited?

CVE-2021-40663 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-2021-40663 affect?

CVE-2021-40663 affects deep.assign. Severity is critical (CVSS 9.8). deep.assign npm package 0.0.0-alpha.0 is vulnerable to Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').

How urgent is CVE-2021-40663?

Priority 64/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

npm packages vulnerabilities

References

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