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Chinese Hackers Exploited Latest SolarWinds 0

criticalExploit / PoCimportance 60CVE-2021-35211

Vulnerabilities mentionedAll →

CVEVulnerabilityCVSSEPSSFlagsAffectedExposurePublished
CVE-2021-35211
Unauthenticated RCE (Remote Memory Escape) in SolarWinds Serv-U

Microsoft researchers discovered a remote code execution flaw in SolarWinds Serv-U, an out-of-bounds write (CWE-787) described as a "Remote Memory Escape" in the Windows-based Serv-U products. A remote, unauthenticated attacker can trigger the flaw over the network against servers running a version before 15.2.3 HF2 and gain privileged access to the machine hosting Serv-U, with a maximum CVSS 10.0 score reflecting no required privileges, no user interaction, and impact beyond the application's security scope. Both Serv-U Managed File Transfer and Serv-U Secure FTP for Windows are affected. The vulnerability has been exploited in the wild: Microsoft attributed July 2021 attacks exploiting the Serv-U zero-day to Chinese threat actors, later warned of an uptick in exploitation attempts, and the flaw was added to CISA KEV on 2021-11-03 with known ransomware use.

Do: Upgrade Serv-U to 15.2.3 Hotfix 2 (HF2) or later per SolarWinds' instructions immediately, as the flaw is in CISA KEV with known exploitation including ransomware use. Audit Serv-U servers and their logs for signs of exploitation or compromise, and restrict internet exposure of Serv-U/FTP and SSH ports to trusted parties.

10.091% KEV ransomware
  • SolarWinds Serv-U Managed File Transfer (Windows) before 15.2.3 HF2
  • SolarWinds Serv-U Secure FTP (Windows) before 15.2.3 HF2
largeestimated tens of thousands of Serv-U deployments worldwide, with a few thousand instances directly internet-exposed
Full article368 words · extracted from thehackernews.com · click to collapse

Ravie LakshmananJul 14, 2021

Microsoft on Tuesday disclosed that the latest string of attacks targeting SolarWinds Serv-U managed file transfer service with a now-patched remote code execution (RCE) exploit is the handiwork of a Chinese threat actor dubbed "DEV-0322."

The revelation comes days after the Texas-based IT monitoring software maker issued fixes for the flaw that could enable adversaries to remotely run arbitrary code with privileges, allowing them to perform actions like install and run malicious payloads or view and alter sensitive data.

Tracked as CVE-2021-35211, the RCE flaw resides in Serv-U's implementation of the Secure Shell (SSH) protocol. While it was previously revealed that the attacks were limited in scope, SolarWinds said it's "unaware of the identity of the potentially affected customers."

Attributing the intrusions with high confidence to DEV-0322 (short for "Development Group 0322") based on observed victimology, tactics, and procedures, Microsoft Threat Intelligence Center (MSTIC) said the adversary is known for targeting entities in the U.S. Defense Industrial Base Sector and software companies.

"This activity group is based in China and has been observed using commercial VPN solutions and compromised consumer routers in their attacker infrastructure," according to MSTIC, which discovered the zero-day after it detected as many as six anomalous malicious processes being spawned from the main Serv-U process, suggesting a compromise.

The development also marks the second time a China-based hacking group has exploited vulnerabilities in SolarWinds software as a fertile field for targeted attacks against corporate networks.

Back in December 2020, Microsoft disclosed that a separate espionage group may have been taking advantage of the IT infrastructure provider's Orion software to drop a persistent backdoor called Supernova on infected systems. The intrusions have since been attributed to a China-linked threat actor called Spiral.

Additional indicators of compromise associated with the attack can be accessed from SolarWinds' revised advisory here.

Update: This article has been updated to reflect that attackers didn't exploit the SolarWinds flaw to target defense and software companies. As of now, no information has been provided on who was attacked during this zero-day attack.

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