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Ransomware criminals have quickly weaponized an easy-to-exploit vulnerability in the PHP programming language that executes malicious code on web servers, security researchers said.

As of Thursday, Internet scans performed by security firm Censys had detected 1,000 servers infected by a ransomware strain known as TellYouThePass, down from 1,800 detected on Monday. The servers, primarily located in China, no longer display their usual content; instead, many list the site’s file directory, which shows all files have been given a .locked extension, indicating they have been encrypted. An accompanying ransom note demands roughly $6,500 in exchange for the decryption key.

The output of PHP servers infected by TellYouThePass ransomware. (credit: Censys)

The accompanying ransom note. (credit: Censys)

When opportunity knocks

The vulnerability , tracked as CVE-2024-4577 and carrying a severity rating of 9.8 out of 10, stems from errors in the way PHP converts Unicode characters into ASCII. A feature built into Windows known as Best Fit allows attackers to use a technique known as argument injection to convert user-supplied input into characters that pass malicious commands to the main PHP application. Exploits allow attackers to bypass CVE-2012-1823, a critical code execution vulnerability patched in PHP in 2012.

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The US Cybersecurity and Infrastructure Security Agency has added a critical security bug in Linux to its list of vulnerabilities known to be actively exploited in the wild.

The vulnerability, tracked as CVE-2024-1086 and carrying a severity rating of 7.8 out of a possible 10, allows people who have already gained a foothold inside an affected system to escalate their system privileges. It’s the result of a use-after-free error, a class of vulnerability that occurs in software written in the C and C++ languages when a process continues to access a memory location after it has been freed or deallocated. Use-after-free vulnerabilities can result in remote code or privilege escalation.

The vulnerability, which affects Linux kernel versions 5.14 through 6.6, resides in the NF_tables, a kernel component enabling the Netfilter , which in turn facilitates a variety of network operations, including packet filtering, network address [and port] translation (NA[P]T), packet logging, userspace packet queueing, and other packet mangling. It was patched in January, but as the CISA advisory indicates, some production systems have yet to install it. At the time this Ars post went live, there were no known details about the active exploitation.

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Google has updated its Chrome browser to patch a high-severity zero-day vulnerability that allows attackers to execute malicious code on end user devices. The fix marks the fifth time this year the company has updated the browser to protect users from an existing malicious exploit.

The vulnerability, tracked as CVE-2024-4671 , is a “use after free,” a class of bug that occurs in C-based programming languages. In these languages, developers must allocate memory space needed to run certain applications or operations. They do this by using “pointers” that store the memory addresses where the required data will reside. Because this space is finite, memory locations should be deallocated once the application or operation no longer needs it.

Use-after-free bugs occur when the app or process fails to clear the pointer after freeing the memory location. In some cases, the pointer to the freed memory is used again and points to a new memory location storing malicious shellcode planted by an attacker’s exploit, a condition that will result in the execution of this code.

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Hackers are assailing websites using a prominent WordPress plugin with millions of attempts to exploit a high-severity vulnerability that allows complete takeover, researchers said.

The vulnerability resides in WordPress Automatic , a plugin with more than 38,000 paying customers. Websites running the WordPress content management system use it to incorporate content from other sites. Researchers from security firm Patchstack disclosed last month that WP Automatic versions 3.92.0 and below had a vulnerability with a severity rating of 9.9 out of a possible 10. The plugin developer, ValvePress, silently published a patch, which is available in versions 3.92.1 and beyond.

Researchers have classified the flaw, tracked as CVE-2024-27956, as a SQL injection, a class of vulnerability that stems from a failure by a web application to query backend databases properly. SQL syntax uses apostrophes to indicate the beginning and end of a data string. By entering strings with specially positioned apostrophes into vulnerable website fields, attackers can execute code that performs various sensitive actions, including returning confidential data, giving administrative system privileges, or subverting how the web app works.

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Software maker Ivanti is urging users of its end-point security product to patch a critical vulnerability that makes it possible for unauthenticated attackers to execute malicious code inside affected networks.

The vulnerability, in a class known as a SQL injection , resides in all supported versions of the Ivanti Endpoint Manager . Also known as the Ivanti EPM, the software runs on a variety of platforms, including Windows, macOS, Linux, Chrome OS, and Internet of Things devices such as routers. SQL injection vulnerabilities stem from faulty code that interprets user input as database commands or, in more technical terms, from concatenating data with SQL code without quoting the data in accordance with the SQL syntax. CVE-2023-39366, as the Ivanti vulnerability is tracked, carries a severity rating of 9.6 out of a possible 10.

“If exploited, an attacker with access to the internal network can leverage an unspecified SQL injection to execute arbitrary SQL queries and retrieve output without the need for authentication,” Ivanti officials wrote Friday in a post announcing the patch availability. “This can then allow the attacker control over machines running the EPM agent. When the core server is configured to use SQL express, this might lead to RCE on the core server.”

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Roughly 11 million Internet-exposed servers remain susceptible to a recently discovered vulnerability that allows attackers with a foothold inside affected networks. Once they're in, attackers compromise the integrity of SSH sessions that form the lynchpin for admins to securely connect to computers inside the cloud and other sensitive environments.

Terrapin, as the vulnerability has been named, came to light two weeks ago in a research paper published by academic researchers. Tracked as CVE-2023-48795, the attack the researchers devised works when attackers have an adversary-in-the-middle attack (also abbreviated as AitM and known as man-in-the-middle or MitM), such as when they’re positioned on the same local network and can secretly intercept communications and assume the identity of both the recipient and the sender.

In those instances, Terrapin allows attackers to alter or corrupt information transmitted in the SSH data stream during the handshake—the earliest connection stage, when the two parties negotiate the encryption parameters they will use to establish a secure connection. As such, Terrapin represents the first practical cryptographic attack targeting the integrity of the SSH protocol itself. It works by targeting BPP ( Binary Packet Protocol), which is designed to ensure AitMs can’t add or drop messages exchanged during the handshake. This prefix truncation attack works when implementations support either the "ChaCha20-Poly1305" or "CBC with Encrypt-then-MAC," cipher modes, which, at the time the paper was published, was found in 77 percent of SSH servers.

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A vulnerability that allows attackers to bypass multifactor authentication and access enterprise networks using hardware sold by Citrix is under mass exploitation by ransomware hackers despite a patch being available for three weeks.

Citrix Bleed, the common name for the vulnerability, carries a severity rating of 9.4 out of a possible 10, a relatively high designation for a mere information-disclosure bug. The reason: the information disclosed can include session tokens, which the hardware assigns to devices that have already successfully provided credentials, including those providing MFA. The vulnerability, tracked as CVE-2023-4966 and residing in Citrix’s NetScaler Application Delivery Controller and NetScaler Gateway, has been under active exploitation since August . Citrix issued a patch on October 10.

Repeat: This is not a drill

Attacks have only ramped up recently, prompting security researcher Kevin Beaumont on Saturday to declare : “This vulnerability is now under mass exploitation.” He went on to say, “From talking to multiple organizations, they are seeing widespread exploitation.”

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End users, admins, and researchers better brace yourselves: The number of apps being patched for zero-day vulnerabilities has skyrocketed this month and is likely to get worse in the following weeks.

People have worked overtime in recent weeks to patch a raft of vulnerabilities actively exploited in the wild, with offerings from Apple, Microsoft, Google, Mozilla, Adobe, and Cisco all being affected since the beginning of the month. The total number of zero-days in September so far is 10, compared with a total of 60 from January through August, according to security firm Mandiant. The company tracked 55 zero-days in 2022 and 81 in 2021.

The number of zero-days tracked this month is considerably higher than the monthly average this year. A sampling of the affected companies and products includes iOS and macOS, Windows, Chrome, Firefox, Acrobat and Reader, the Atlas VPN, and Cisco’s Adaptive Security Appliance Software and its Firepower Threat Defense. The number of apps is likely to grow because a single vulnerability that allows hackers to execute malicious code when users open a booby-trapped image included in a message or web page is present in possibly hundreds of apps.

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A newly discovered zeroday in the widely used WinRAR file-compression program has been under exploit for four months by unknown attackers who are using it to install malware when targets open booby-trapped JPGs and other innocuous inside file archives.

The vulnerability, residing in the way WinRAR processes the ZIP file format, has been under active exploit since April in securities trading forums, researchers from security firm Group IB reported Wednesday . The attackers have been using the vulnerability to remotely execute code that installs malware from families including DarkMe, GuLoader, and Remcos RAT.

From there, the criminals withdraw money from broker accounts. The total amount of financial losses and total number of victims infected is unknown, although Group-IB said it has tracked at least 130 individuals known to have been compromised. WinRAR developers fixed the vulnerability, tracked as CVE-2023-38831, earlier this month.