U.S. Cybersecurity Agency Adds 6 Flaws to Known Exploited Vulnerabilities Catalog

An out-of-bounds write issue was addressed with improved input validation. This issue is fixed in iOS 16.2 and iPadOS 16.2, macOS Ventura 13.1, tvOS 16.2, watchOS 9.2. An app may be able to execute arbitrary code with kernel privileges.

VMware Tools, the agent installed inside guest virtual machines, fails to properly authenticate host-to-guest operations when they are issued from an ESXi host (CVE-2023-20867, CWE-287 improper authentication). An attacker who has already gained full (root) control of an ESXi host can invoke these operations, such as running commands or moving files inside guest VMs, and the guests' VMware Tools will accept them without valid authentication. This gives an attacker a foothold in guest VMs without guest credentials, affecting guest confidentiality and integrity. Any organization running VMware ESXi/vSphere with VMware Tools in its guests is affected, and the component is also shipped as open-vm-tools in Debian and Fedora. The flaw is confirmed exploited in the wild: CISA added it to the Known Exploited Vulnerabilities catalog on 2023-06-23 (EPSS 13.5%, 96th percentile), and China-linked APT UNC3886, whose 'Fire Ant' tooling targets ESXi and vCenter, has been reported using it alongside other VMware flaws.

Do: Upgrade VMware Tools / open-vm-tools to the latest fixed release distributed by VMware, Debian, or Fedora per the vendor advisory, and inventory guests running outdated Tools. Because exploitation requires a fully compromised ESXi host, hunt for signs of host compromise (unexpected processes, modified VIBs, suspicious vCenter activity) and review guest VMs for unexplained command execution or persistence. Consistent with the KEV required action, prioritize patching, starting with internet-facing ESXi hosts and virtualization management infrastructure.

VMware Aria Operations for Networks (formerly vRealize Network Insight) contains a command injection flaw (CWE-77) that allows an attacker with network access to the appliance to run arbitrary operating-system commands. Because the attack requires no authentication, privileges, or user interaction (CVSS:3.1/AV:N/AC:L/PR:N/UI:N), any party able to reach the product's network interface can trigger it, gaining remote code execution with high impact on confidentiality, integrity, and availability. Any organization running the product is affected, with internet-facing deployments at the greatest risk. Exploitation is confirmed in the wild — CISA added the flaw to the KEV catalog on 2023-06-22, a public proof-of-concept exploit is available, and EPSS puts the 30-day exploitation probability at 98.3% (top percentile). Ransomware use is currently unknown.

Do: Apply the vendor's patched update to all Aria Operations for Networks deployments as soon as possible — this is also CISA's required KEV action (apply updates per vendor instructions); verify the installed build against VMware's advisory for affected ranges. Until patching is complete, restrict network access to the appliance (firewall rules, VPN, or management-segment isolation), prioritizing any instance reachable from the internet since no authentication is required to exploit. Hunt for indicators of command injection exploitation, as in-the-wild exploitation has been confirmed.

Zyxel NAS326, NAS540, and NAS542 network-attached storage devices contain a pre-authentication command injection flaw (CWE-78) that lets an unauthenticated attacker execute operating system commands by sending a crafted HTTP request to the device. Because the flaw is network-facing and requires no credentials or user interaction, a remote attacker gains the ability to run arbitrary OS commands on the device, effectively full compromise. Affected firmware is NAS326 versions prior to V5.21(AAZF.14)C0, NAS540 versions prior to V5.21(AATB.11)C0, and NAS542 versions prior to V5.21(ABAG.11)C0. The flaw scores 9.8 (critical) on CVSS 3.1, carries a very high 83.8% probability of exploitation within 30 days per EPSS, and CISA added it to the Known Exploited Vulnerabilities catalog on 2023-06-23. News reporting indicates a Mirai-like botnet is already exploiting the flaw in the wild, so defenders should treat it as an actively exploited, internet-exposable issue and patch immediately.

Do: Upgrade NAS326 to V5.21(AAZF.14)C0, NAS540 to V5.21(AATB.11)C0, and NAS542 to V5.21(ABAG.11)C0 per Zyxel's security advisories. Until patched, keep the NAS web administration interface off the public internet or restrict access with firewall rules. Because a Mirai-like botnet is actively exploiting this flaw, inspect patched and unpatched devices for signs of compromise, such as unfamiliar processes or unexpected outbound traffic; organizations covered by CISA's KEV requirements must apply the vendor updates by the required deadline.

Every `named` instance configured to run as a recursive resolver maintains a cache database holding the responses to the queries it has recently sent to authoritative servers. The size limit for that cache database can be configured using the `max-cache-size` statement in the configuration file; it defaults to 90% of the total amount of memory available on the host. When the size of the cache reaches 7/8 of the configured limit, a cache-cleaning algorithm starts to remove expired and/or least-recently used RRsets from the cache, to keep memory use below the configured limit. It has been discovered that the effectiveness of the cache-cleaning algorithm used in `named` can be severely diminished by querying the resolver for specific RRsets in a certain order, effectively allowing the configured `max-cache-size` limit to be significantly exceeded. This issue affects BIND 9 versions 9.11.0 through 9.16.41, 9.18.0 through 9.18.15, 9.19.0 through 9.19.13, 9.11.3-S1 through 9.16.41-S1, and 9.18.11-S1 through 9.18.15-S1.

Apple's WebKit engine, used by Safari and shipped with iOS, iPadOS, and macOS, contains a type confusion vulnerability (CWE-843) that leads to code execution when processing maliciously crafted web content. An attacker can trigger the flaw by inducing a victim to load attacker-controlled web content, for example by visiting a crafted webpage or opening malicious HTML in any application that renders it with WebKit. Successful exploitation grants the attacker arbitrary code execution within the web-content processing context of the affected browser or application. The exposure is broad: every iPhone, iPad, and Mac running vulnerable WebKit builds is affected, and the flaw could also impact HTML parsers in non-Apple products that rely on WebKit. The vulnerability was added to CISA's Known Exploited Vulnerabilities catalog on 2023-06-23, confirming known in-the-wild exploitation (ransomware use unknown); no public proof-of-concept is known, and CISA's required action is to apply updates per vendor instructions.

Do: Apply Apple's security updates for iOS, iPadOS, macOS, and Safari immediately, following vendor instructions as required by the CISA KEV catalog, since the flaw is confirmed exploited in the wild. Administrators should also inventory any non-Apple applications, HTML parsers, or embedded browsers that use WebKit and apply the corresponding vendor patches when available. Until patching is complete, treat unsolicited web links and HTML content as a primary attack vector and prioritize updates on internet-facing and user-facing Apple systems.