CISA adds flaw in Citrix ShareFile to its Known Exploited Vulnerabilities catalog

Pierluigi Paganini August 16, 2023

US CISA added critical vulnerability CVE-2023-24489 in Citrix ShareFile to its Known Exploited Vulnerabilities catalog.

US Cybersecurity and Infrastructure Security Agency (CISA) added critical flaw CVE-2023-24489 (CVSS score 9.8) affecting Citrix ShareFile to its Known Exploited Vulnerabilities Catalog.

Citrix ShareFile is a secure file sharing and storage platform designed for businesses and professionals to collaborate on documents, exchange files, and manage content in a secure and efficient manner.

Citrix Content Collaboration is affected by an improper access control issue that can allow a remote, unauthenticated attacker to compromise customer-managed ShareFile storage zones controllers

Citrix addressed the vulnerability in June 2023 with the release of version 5.11.24.

“A vulnerability has been discovered in the customer-managed ShareFile storage zones controller which, if exploited, could allow an unauthenticated attacker to remotely compromise the customer-managed ShareFile storage zones controller.” the company said in an advisory. “This vulnerability affects all currently supported versions of customer-managed ShareFile storage zones controller before version 5.11.24.”

Researchers from threat intelligence firm Greynoise warned at the end of July of the first attempts to exploit the vulnerability in Citrix ShareFile.

“Attackers can exploit this vulnerability by taking advantage of errors in ShareFile’s handling of cryptographic operations. The application uses AES encryption with CBC mode and PKCS7 padding but does not correctly validate decrypted data.” states Greynoise. “This oversight allows attackers to generate valid padding and execute their attack, leading to unauthenticated arbitrary file upload and remote code execution.”

“As of the publishing timestamp of this post, GreyNoise has observed IPs attempting to exploit this vulnerability. Two have never seen GreyNoise before this activity” adds GreyNoise.

Citrix ShareFile

Researchers at the cybersecurity firm Assetnote published technical details of the vulnerability and published proof-of-concept (PoC) code for this flaw.

“A search online shows roughly 1000-6000 instances are internet accessible. This popularity, combined with the software being used to store sensitive data, meant if we found anything it could have quite an impact.” reads the analysis published by Assetnote.

Other PoC exploits have been published online, for this reason, experts warn that the number of attacks exploiting this issue will rapidly increase in the forthcoming days.

“we saw how a few small errors in ShareFile lead to an unauthenticated file upload and then remote code execution. Although the particular endpoint is not enabled in all configurations, it has been common amongst the hosts we have tested.” concludes Assetnote. “Given the number of instances online and the reliability of the exploit, we have already seen a big impact from this vulnerability.”

GreyNoisesearchers reported a huge spike in exploit activity today.

According to Binding Operational Directive (BOD) 22-01: Reducing the Significant Risk of Known Exploited Vulnerabilities, FCEB agencies have to address the identified vulnerabilities by the due date to protect their networks against attacks exploiting the flaws in the catalog.

Experts recommend also private organizations review the Catalog and address the vulnerabilities in their infrastructure.

CISA orders federal agencies to fix this flaw by September 6, 2023.

Update August 16, 2023

The company contacted Security Affairs to provide the following update:

  • Timeline:  
  • A fix for CVE-2023-24489 was released on May 11, 2023 with Version 5.11.24 (one month before the security bulletin was issued). 
  • Customer patching was proactively handled and, by June 13, over 83% of these customers had patched their environments, before the incident was made public. Also, by June 13, all unpatched SZC hosts were blocked from connecting to the ShareFile cloud control plane, making unpatched SZC hosts unusable with ShareFile.
  • On Aug. 16, CISA added the CVE to their known exploited vulnerability catalog; while there was a spike to 75 attacks following this, this died down immediately given that the issue has been addressed.
  • Impact of Incident
  • When this vulnerability was discovered, we worked with and notified impacted customers in advance of the announced CVE to update to the latest version of our software to assure the safety of their data. Our control plane is no longer connected to any ShareFile StorageZones Controller (SZC) that is not patched. 
  • The incident affected less than 3% of our install base (2800 customers)
  • There is no known data theft from this incident

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Pierluigi Paganini

(SecurityAffairs – hacking, CISA)

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