How severe is CVE-2021-3757?

CVE-2021-3757 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-3757 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (74th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3757?

CVE-2021-3757 affects Immer Project Immer. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3757?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-3757 published?

CVE-2021-3757 was published on 2021-09-02 and last updated on 2026-06-17.

CVE-2021-3757

CVE-2021-3757 is a critical-severity vulnerability in Immer Project Immer with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-1321.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (74th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-1321
Affected product: Immer Project Immer
Published: 2021-09-02
Last modified: 2026-06-17

Description

immer is vulnerable to Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Frequently asked questions

What is CVE-2021-3757?: immer is vulnerable to Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
How severe is CVE-2021-3757?: CVE-2021-3757 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-3757 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (74th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3757?: CVE-2021-3757 affects Immer Project Immer. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3757?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-3757 published?: CVE-2021-3757 was published on 2021-09-02 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:immer_project:immer:*:*:*:*:*:node.js:*:*

More vulnerabilities in Immer Project Immer

CVE-2020-28477 — High (CVSS 7.5): This affects all versions of package immer.
CVE-2021-23436 — Medium (CVSS 5.6): This affects the package immer before 9.0.6. A type confusion vulnerability can lead to a bypass of CVE-2020-28477 when…

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CVE-2024-39008 — Critical (CVSS 10.0): robinweser fast-loops v1.1.3 was discovered to contain a prototype pollution via the function objectMergeDeep. This…
CVE-2024-38999 — Critical (CVSS 10.0): jrburke requirejs v2.3.6 was discovered to contain a prototype pollution via the function s.contexts._.configure. This…
CVE-2022-29823 — Critical (CVSS 10.0): Feather-Sequalize cleanQuery method uses insecure recursive logic to filter unsupported keys from the query object.…
CVE-2022-24760 — Critical (CVSS 10.0): Parse Server is an open source http web server backend. In versions prior to 4.10.7 there is a Remote Code Execution…
CVE-2020-12079 — Critical (CVSS 10.0): Beaker before 0.8.9 allows a sandbox escape, enabling system access and code execution. This occurs because Electron…

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