CVE-2021-43787Public exploitNetwork attack vector

Account takeover via uploader prototype pollution

Published Nov 29, 2021 · Updated Aug 4, 2024

Cross-site scripting in NodeBB 1.15.5 through 1.18.4 allows remote authenticated users to execute JavaScript in visitors' browsers. The Socket.IO uploads.upload handler accepts data.params.method through an inherited-property lookup and stores per-socket upload state in a prototype-bearing object, allowing crafted keys to alter prototype-backed state. Exploitation requires a logged-in attacker, the companion translator path traversal, and a visitor who loads the poisoned content, enabling account takeover.

CVSS severity6.1
Medium
EPSS probability1.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in NodeBB 1.15.5 through 1.18.4 allows remote authenticated users to execute JavaScript in visitors' browsers. The Socket.IO uploads.upload handler accepts data.params.method through an inherited-property lookup and stores per-socket upload state in a prototype-bearing object, allowing crafted keys to alter prototype-backed state. Exploitation requires a logged-in attacker, the companion translator path traversal, and a visitor who loads the poisoned content, enabling account takeover.

The record

CVE
CVE-2021-43787
Published
Nov 29, 2021
Updated
Aug 4, 2024
Vendor
NodeBB
Product
NodeBB
Classifications
CWE-79, CWE-1321, T1189
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 29, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=>= 1.15.5, < 1.18.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

NodeBB · NodeBBversion=>= 1.15.5, < 1.18.5

Published CVSS scores

9.0GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
T1189Drive-by Compromise

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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