CVE-2020-28477Public exploitNetwork attack vector

Service interruption via unsafe patch path traversal

Published Jan 19, 2021 · Updated Sep 17, 2024

Prototype pollution in Immer before 8.0.1 allows remote attackers to interrupt consuming applications via crafted patches. The applyPatches_ function follows attacker-controlled path segments such as proto or constructor into inherited objects and assigns supplied values without rejecting reserved attributes. Exploitation requires a consuming application to enable patches and pass attacker-controlled patch objects; the resulting effect depends on how polluted properties are used.

CVSS severity7.5
High
EPSS probability2.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Prototype pollution in Immer before 8.0.1 allows remote attackers to interrupt consuming applications via crafted patches. The applyPatches_ function follows attacker-controlled path segments such as proto or constructor into inherited objects and assigns supplied values without rejecting reserved attributes. Exploitation requires a consuming application to enable patches and pass attacker-controlled patch objects; the resulting effect depends on how polluted properties are used.

The record

CVE
CVE-2020-28477
Published
Jan 19, 2021
Updated
Sep 17, 2024
Vendor
Michel Weststrate
Product
Immer
Classifications
CWE-1321, CWE-471
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 19, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <unspecified

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Michel Weststrate · Immerversion=0 <unspecified

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
CWE-471Modification of Assumed-Immutable Data (MAID)

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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