Experts warn attackers started exploiting Citrix ShareFile RCE flaw
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2023-24489 | Unauthenticated RCE in Citrix ShareFile Storage Zones Controller (CVE-2023-24489) CVE-2023-24489 is an improper access control flaw (CWE-284), rated critical at CVSS 9.8, in the customer-managed Citrix Content Collaboration ShareFile storage zones controller. It can be triggered remotely over the network by an unauthenticated attacker with no privileges and no user interaction (AV:N/AC:L/PR:N/UI:N). A successful attack allows the attacker to remotely compromise the customer-managed storage zones controller — described in vendor-adjacent coverage as remote code execution — giving control of the server that stores and syncs that organization's ShareFile files. Only organizations that self-host customer-managed storage zones controllers are affected; the vendor-managed (cloud) ShareFile service is not listed as affected. The flaw is being actively exploited in the wild: CISA added it to the KEV catalog on 2023-08-16, EPSS assigns a 97.3% probability of exploitation within 30 days (100th percentile), and the vendor urged customers to shut down or take unpatched controllers offline; ransomware use is not yet confirmed. Do: Apply the fix specified in the Citrix/ShareFile security bulletin by upgrading every customer-managed storage zones controller to the vendor's patched release, and follow vendor guidance to shut down or take offline any controller that cannot be patched immediately. Check whether controllers are internet-exposed and hunt for signs of compromise (unexpected files, processes, or webshells on storage zones), since the flaw is in the KEV catalog and ransomware use has not been ruled out. | 9.8 | 97% | KEV |
| moderate≈ thousands of internet-exposed customer-managed storage zone controllers (order-of-magnitude estimate) |
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Researchers warn that threat actors started exploiting Citrix ShareFile RCE vulnerability CVE-2023-24489 in the wild.
Citrix ShareFile is a widely used cloud-based file-sharing application, which is affected by the critical remote code execution (RCE) tracked as CVE-2023-24489 (CVSS score of 9.1).
The flaw impacts the customer-managed ShareFile storage zones controller, an unauthenticated, remote attacker can trigger the flaw to compromise the controller by uploading arbitrary file or executing arbitrary code.
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 warn 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.
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.”
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