CVE-2021-31800

published 2021-05-05

CVE-2021-31800: Multiple path traversal vulnerabilities exist in smbserver.py in Impacket through 0.9.22. An attacker that connects to a running smbserver instance can list…

Priority P2 69 critical 9.8 CVSS 3.1

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

Multiple path traversal vulnerabilities exist in smbserver.py in Impacket through 0.9.22. An attacker that connects to a running smbserver instance can list and write to arbitrary files via ../ directory traversal. This could potentially be abused to achieve arbitrary code execution by replacing /etc/shadow or an SSH authorized key.

Affected

10 ranges

Vendor	Product	Version range	Fixed in
debian	impacket	< impacket 0.9.22-2 (bookworm)	impacket 0.9.22-2 (bookworm)
fedoraproject	fedora	—	—
fedoraproject	fedora	—	—
fedoraproject	fedora	—	—
secureauth	impacket	<= 0.9.22	—
secureauth	impacket	>= 0 < 0.9.22-2	0.9.22-2
secureauth	impacket	>= 0 < 0.9.22-2	0.9.22-2
secureauth	impacket	>= 0 < 0.9.22-2	0.9.22-2
secureauth	impacket	>= 0 < 0.9.22-2	0.9.22-2
secureauth	impacket	>= 0 < 0.9.23	0.9.23

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

• → Path traversal attempts using '../' sequences in SMB requests to a running Impacket smbserver instance should be flagged as malicious ↗
• → Monitor for unauthorized writes to sensitive files such as /etc/shadow or SSH authorized_keys files, which may indicate exploitation of this vulnerability for privilege escalation or persistence ↗

• · Vulnerability affects Impacket smbserver.py through version 0.9.22 only; fixed in 0.9.22-2 (Debian packages). Verify the running Impacket version before applying detection logic. ↗
• · The vulnerability is scoped as local (attacker must be able to connect to the running smbserver instance), limiting remote exploitation surface. ↗

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 7.5 HIGH AV:N/AC:L/Au:N/C:P/I:P/A:P

osv 9.8 CRITICAL

vendor_debian 9.8 CRITICAL

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CWE-22