CVE-2023-26133Network attack vector

Prototype pollution via unsafe property copy

Published Jun 12, 2023 · Updated Jan 6, 2025

Prototype Pollution in progressbar.js before 1.1.1 allows attackers to alter JavaScript object prototypes via crafted input. The extend function in src/utils.js iterates source properties and assigns each value to the destination without blocking prototype-mutating keys such as proto, enabling pollution of shared object state. Exploitation requires a consuming application to pass attacker-controlled data into this merge routine; resulting integrity or availability effects depend on downstream gadgets.

CVSS severity9.8
Critical
EPSS probability1.25%
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 progressbar.js before 1.1.1 allows attackers to alter JavaScript object prototypes via crafted input. The extend function in src/utils.js iterates source properties and assigns each value to the destination without blocking prototype-mutating keys such as proto, enabling pollution of shared object state. Exploitation requires a consuming application to pass attacker-controlled data into this merge routine; resulting integrity or availability effects depend on downstream gadgets.

The record

CVE
CVE-2023-26133
Published
Jun 12, 2023
Updated
Jan 6, 2025
Vendor
Kimmo Brunfeldt
Product
progressbar.js
Classifications
CWE-1321, T1129
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 12, 2023CVE publishedPublication date reported by the CVE source.
  2. Jan 6, 2025Record 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 <*

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Kimmo Brunfeldt · progressbar.jsversion=0 <*

Published CVSS scores

9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
8.2SnykCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L/E:P

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
T1129Shared Modules

Public exploit references

No public exploit references are available in this record.

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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