Critical Patch Released for 'Wormable' SMBv3 Vulnerability — Install It ASAP!
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2020-0796 | Unauthenticated RCE in Microsoft SMBv3 (SMBGhost) CVE-2020-0796 ('SMBGhost') is a memory-corruption (CWE-119) flaw in Microsoft's Server Message Block 3.1.1 (SMBv3) implementation, in which certain crafted requests — notably malformed compressed SMBv3 messages — can corrupt memory on the target. An unauthenticated remote attacker can trigger it by sending specially crafted SMBv3 packets directly to any SMB-enabled host, with no credentials or user interaction required. Successful exploitation yields arbitrary code execution on the target server or client, giving the attacker full control of the host, and the flaw was widely characterized as wormable because a compromised host can then attack others. Any Windows system running SMBv3 is affected — SMBv3 is enabled by default on modern Windows 10 and Windows Server builds, with Windows 10 versions 1903/1909 and Windows Server 2019/versions 1903/1909 identified in Microsoft's advisory. Exploitation is confirmed in the wild: the CVE is in CISA KEV (added 2022-02-10) with known ransomware use, EPSS assigns a 99.8% probability of exploitation within 30 days (100th percentile), and no public PoC is listed in the source data. Do: Apply Microsoft's updates per vendor instructions immediately, prioritizing Windows 10 1903/1909 and Windows Server 2019/1903/1909 hosts and anything with SMB (TCP 445) reachable by untrusted networks. Until patched, disable SMBv3 compression per Microsoft's mitigation guidance (setting DisableCompression=1 under LanmanServer) and restrict inbound TCP 445 to trusted sources. Given confirmed ransomware use, hunt for post-exploitation activity on unpatched hosts. | 10.0 | 100% | KEV ransomware PoC ×2 |
| masstens of millions of Windows hosts with SMBv3 enabled; on the order of 1M+ hosts with SMB (TCP 445) exposed to the internet per public scans |
Full article428 words · extracted from thehackernews.com · click to collapse
The Hacker NewsMar 12, 2020
Microsoft today finally released an emergency software update to patch the recently disclosed very dangerous vulnerability in SMBv3 protocol that could let attackers launch wormable malware, which can propagate itself from one vulnerable computer to another automatically.
The vulnerability, tracked as CVE-2020-0796, in question is a remote code execution flaw that impacts Windows 10 version 1903 and 1909, and Windows Server version 1903 and 1909.
Server Message Block (SMB), which runs over TCP port 445, is a network protocol that has been designed to enable file sharing, network browsing, printing services, and interprocess communication over a network.
The latest vulnerability, for which a patch update (KB4551762) is now available on the Microsoft website, exists in the way SMBv3 protocol handles requests with compression headers, making it possible for unauthenticated remote attackers to execute malicious code on target servers or clients with SYSTEM privileges.
Compression headers is a feature that was added to the affected protocol of Windows 10 and Windows Server operating systems in May 2019, designed to compress the size of messages exchanged between a sever and clients connected to it.
"To exploit the vulnerability against a server, an unauthenticated attacker could send a specially crafted packet to a targeted SMBv3 server. To exploit the vulnerability against a client, an unauthenticated attacker would need to configure a malicious SMBv3 server and convince a user to connect to it," Microsoft said in the advisory.
At the time of writing, there is only one known PoC exploit that exists for this critical remotely exploitable flaw, but reverse engineering new patches could now also help hackers find possible attack vectors to develop fully weaponized self-propagating malware.
A separate team of researchers have also published a detailed technical analysis of the vulnerability, concluding a kernel pool overflow as the root cause of the issue.
As of today, there are nearly 48,000 Windows systems vulnerable to the latest SMB compression vulnerability and accessible over the Internet.
Since a patch for the wormable SMBv3 flaw is now available to download for affected versions of Windows, it's highly recommended for home users and businesses to install updates as soon as possible, rather than merely relying on the mitigation.
In cases where immediate patch update is not applicable, it's advised to at least disable SMB compression feature and block SMB port for both inbound and outbound connections to help prevent remote exploitation.
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Text extracted automatically; images, tables and formatting may be missing. Original: https://thehackernews.com/2020/03/patch-wormable-smb-vulnerability.html