CVE-2021-20680Network attack vector

Unauthenticated browser script execution

Published Apr 26, 2021 · Updated Aug 3, 2024

Cross-site scripting in affected NEC Aterm firmware allows remote attackers to execute arbitrary script in a user's browser via a crafted URL. The published advisories associate the flaw with the web-based management browsing context but do not disclose the input, page, or output-encoding failure. Exploitation requires a user to open attacker-controlled content while the browser can reach the device, enabling script execution in that browser context.

CVSS severity6.1
Medium
EPSS probability0.80%
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 affected NEC Aterm firmware allows remote attackers to execute arbitrary script in a user's browser via a crafted URL. The published advisories associate the flaw with the web-based management browsing context but do not disclose the input, page, or output-encoding failure. Exploitation requires a user to open attacker-controlled content while the browser can reach the device, enabling script execution in that browser context.

The record

CVE
CVE-2021-20680
Published
Apr 26, 2021
Updated
Aug 3, 2024
Vendor
NEC Platforms, Ltd.
Product
Aterm
Classifications
CWE-79, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=Aterm WG1900HP2 firmware Ver.1.3.1 and earlier, Aterm WG1900HP firmware Ver.2.5.1 and earlier, Aterm WG1800HP4 firmware Ver.1.3.1 and earlier, Aterm WG1800HP3 firmware Ver.1.5.1 and earlier, Aterm WG1200HS2 firmware Ver.2.5.0 and earlier, Aterm WG1200HP3 firmware Ver.1.3.1 and earlier, Aterm WG1200HP2 firmware Ver.2.5.0 and earlier, Aterm W1200EX firmware Ver.1.3.1 and earlier, Aterm W1200EX-MS firmware Ver.1.3.1 and earlier, Aterm WG1200HS firmware all versions Aterm WG1200HP firmware all versions Aterm WF800HP firmware all versions Aterm WF300HP2 firmware all versions Aterm WR8165N firmware all versions Aterm W500P firmware all versions, and Aterm W300P firmware all versions

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

NEC Platforms, Ltd. · Atermversion=Aterm WG1900HP2 firmware Ver.1.3.1 and earlier, Aterm WG1900HP firmware Ver.2.5.1 and earlier, Aterm WG1800HP4 firmware Ver.1.3.1 and earlier, Aterm WG1800HP3 firmware Ver.1.5.1 and earlier, Aterm WG1200HS2 firmware Ver.2.5.0 and earlier, Aterm WG1200HP3 firmware Ver.1.3.1 and earlier, Aterm WG1200HP2 firmware Ver.2.5.0 and earlier, Aterm W1200EX firmware Ver.1.3.1 and earlier, Aterm W1200EX-MS firmware Ver.1.3.1 and earlier, Aterm WG1200HS firmware all versions Aterm WG1200HP firmware all versions Aterm WF800HP firmware all versions Aterm WF300HP2 firmware all versions Aterm WR8165N firmware all versions Aterm W500P firmware all versions, and Aterm W300P firmware all versions

Published CVSS scores

4.3JPCERT/CC and IPAAV:N/AC:M/Au:N/C:N/I:P/A:N
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
6.1JPCERT/CC and IPACVSS:3.0/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')
T1189Drive-by Compromise

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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