CVE-2021-20091Public exploitNetwork attack vector

Authenticated remote code execution via configuration newline injection

Published Apr 29, 2021 · Updated Aug 3, 2024

Configuration injection in Buffalo WSR-2533 routers allows remote authenticated users to execute code through crafted web parameters. Parameters handled by apply_abstract.cgi are written into /tmp/etc/config/.glbcfg without rejecting encoded newlines, so a supplied ping address can add a setting that enables telnetd after reboot. Access requires a valid session and token; successful exploitation alters persistent device configuration and exposes a shell on TCP port 23.

CVSS severity8.8
High
EPSS probability8.80%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Configuration injection in Buffalo WSR-2533 routers allows remote authenticated users to execute code through crafted web parameters. Parameters handled by apply_abstract.cgi are written into /tmp/etc/config/.glbcfg without rejecting encoded newlines, so a supplied ping address can add a setting that enables telnetd after reboot. Access requires a valid session and token; successful exploitation alters persistent device configuration and exposes a shell on TCP port 23.

The record

CVE
CVE-2021-20091
Published
Apr 29, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1059
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 29, 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

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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 privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
6.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A: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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1059Command and Scripting Interpreter

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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