CVE-2021-46251Network attack vector

Script execution via unescaped invalid username

Published Feb 15, 2022 · Updated Aug 4, 2024

Reflected XSS in ScratchOAuth2 allows remote attackers to run arbitrary scripts in a user's browser through a crafted POST request. The specialLogin method inserts an invalid username into an error message with plain rendering instead of treating the username as a plaintext parameter. Exploitation requires user interaction with the reflected response; the injected content executes in the page's browser origin and can read or modify page data.

CVSS severity6.1
Medium
EPSS probability0.56%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in ScratchOAuth2 allows remote attackers to run arbitrary scripts in a user's browser through a crafted POST request. The specialLogin method inserts an invalid username into an error message with plain rendering instead of treating the username as a plaintext parameter. Exploitation requires user interaction with the reflected response; the injected content executes in the page's browser origin and can read or modify page data.

The record

CVE
CVE-2021-46251
Published
Feb 15, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 15, 2022CVE 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

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1MITRECVSS: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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

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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