Very swiftly after disclosing them, Citrix has issued patches for two vulnerabilities in its Citrix Digital Apps and Desktop know-how that enable a distant attacker escalate privileges or execute code of their selection on weak methods.
Citrix has described the distant code execution (RCE) vulnerabilities as one thing that solely a beforehand authenticated attacker may abuse. Nonetheless, researchers at watchTowr who found the failings and developed a proof-of-concept exploit (PoC) say it is a point-and-click vulnerability that an unauthenticated attacker can exploit with relative ease.
Citrix is monitoring one of many flaws as CVE-2024-8068 and the opposite as CVE-2024-8069.
Citrix Downplaying Menace Severity?
The failings have an effect on the thin-client know-how’s Session Recording Supervisor part that enables admins to seize, retailer, and handle recordings of consumer classes. They stem from a weak spot in how Session Recording Supervisor deserializes or unpacks knowledge that has been transformed right into a format that makes it simple to retailer and transmit, in line with the researchers at watchTowr who found and reported the problems to Citrix in July.
Citrix initially mentioned it was unable to breed the difficulty however later acknowledged the issue after the safety vendor gave them a PoC exploit for the vulnerability.
In an advisory issued Nov. 12, the corporate described CVE-2024-8068 as a privilege escalation vulnerability that enables an authenticated consumer in the identical Home windows Lively Listing area because the session recording server to achieve NetworkService Account entry. CVE-2024-8069, in line with Citrix, is a “restricted” RCE for attackers with admin-level account entry on weak methods. “Cloud Software program Group strongly urges affected clients of Citrix Session Recording to put in the related up to date variations of Citrix Session Recording as quickly their improve schedule permits,” the corporate cautioned.
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Even so, Citrix has assigned each vulnerabilities solely medium severity scores of 5.1 of 10 on the CVSS vulnerability ranking scale. It is an project that watchTowr has disputed.
“Citrix is downplaying the severity of this vulnerability as a medium precedence when it’s actually point-click-full-takeover,” says Benjamin Harris, CEO of watchTowr, pointing to the corporate’s exploit code. The mix of the 2 vulnerabilities permits for a “good previous unauthenticated RCE,” Harris tells Darkish Studying.
“Citrix’s Digital Apps and Desktop providing is a flagship Citrix resolution, focused at [Fortune 500] organizations,” he notes. “Since we’re coping with a deserialization difficulty, a bug class that’s recognized for being comparatively steady, we [have] a excessive diploma of confidence that our exploit will work reliably. There isn’t any difficult heap manipulation or different entropy creeping in.”
Many organizations use Citrix’s Digital Apps and Desktop know-how to allow customers to entry their purposes and desktop environments from wherever and utilizing any gadget. It provides organizations a method to centrally deploy, replace, and safe all consumer apps from a single location making upkeep extra environment friendly, constant, and price efficient. One other profit that Citrix advertises is elevated safety from having purposes and knowledge on centralized servers moderately than on particular person endpoint units. The know-how’s Session Recording characteristic — the place watchTowr found the failings — permits admins to observe for anomalous conduct and to take care of an in depth file of consumer exercise for future audit and troubleshooting functions.
Demand for such applied sciences has elevated in recent times as extra corporations have embraced distant and hybrid work fashions. Analysis agency MarketsandMarkets estimates the market will attain $1.7 billion in 2028 from round $1.5 billion final 12 months. The broader desktop-as-a-service (DaaS) market itself is predicted to hit almost $19 billion by 2030 from simply over $4 billion in 2021.
Dependence on Recognized Insecure Expertise
The researchers at watchTowr found the vulnerabilities whereas scrutinizing Citrix’s Digital Apps and Desktop’s structure for potential safety points. The safety vendor’s examination confirmed that Citrix’s app makes use of Microsoft’s Message Queuing (MSMQ) service to obtain recorded consumer session recordsdata and to retailer them in a separate storage supervisor part. As well as, watchTowr discovered Citrix utilizing a Microsoft know-how known as BinaryFormatter to deserialize knowledge within the storage supervisor part when wanted. BinaryFormatter is know-how that Microsoft itself has urged organizations to cease utilizing as quickly as attainable due to safety weaknesses which can be not fixable, watchTowr mentioned.
The vulnerabilities that watchTowr found concerned a mix of an Web-accessible MSMQ occasion within the session recording part of Citrix’s Digital Apps and Desktop know-how together with misconfigured permissions associated to BinaryFormatter. “This is not actually a bug within the BinaryFormatter itself, nor a bug in MSMQ, however moderately the unlucky consequence of Citrix counting on the documented-to-be-insecure BinaryFormatter to take care of a safety boundary,” Harris says. “It is a ‘bug’ that manifested throughout the design part, when Citrix determined which serialization library to make use of.”
Harris says watchTowr reported the vulnerability as a single difficulty, whereas Citrix seems to have handled it as two separate points.
“Whereas it’s inarguable that Citrix’s use of a BinaryFormatter with untrusted knowledge is a de facto bug,” Harris says, “we do not have sufficient context to find out if exposing the MSMQ queue by way of HTTP is mostly a bug, attributable to a careless oversight, or a fastidiously calculated impact of some obscure enterprise requirement.”
Citrix’s applied sciences are a frequent goal for attackers due to the excessive degree of entry the corporate’s know-how supplies to enterprise purposes and knowledge. Most of the reported safety flaws lately have affected the corporate’s NetScaler ADC and NetScaler Gateway distant entry platforms.