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Overview
Tunnelling protocols are an essential part of the Internet and form much of the backbone that modern network infrastructure relies on today. One limitation of these protocols is that they do not authenticate and/or encrypt traffic. Though this limitation exists, IPsec can be implemented to help prevent attacks. However, implementation of these protocols have been executed poorly in some areas.
For the latest security findings from the researchers at the DistriNet-KU Leuven research group, please refer to: https://papers.mathyvanhoef.com/usenix2025-tunnels.pdf
Description
Researchers at the DistriNet-KU Leuven research group have discovered millions of vulnerable Internet systems that accept unauthenticated IPIP, GRE, 4in6, or 6in4 traffic. This can be considered a generalization of the vulnerability in VU#636397 : IP-in-IP protocol routes arbitrary traffic by default (CVE-2020-10136). The exposed systems can be abused as one-way proxies, enable an adversary to spoof the source address of packets (CWE-290 Authentication Bypass by Spoofing), or permit access to an organization’s private network. Vulnerable systems can also facilitate Denial-of-Service (DoS) attacks.
Two types of DoS attacks exploiting this vulnerability can amplify traffic: one concentrates traffic in time (“Tunneled-Temporal Lensing”), and the other can loop packets between vulnerable systems, resulting in an amplification factor of at least 13- and 75-fold, respectively. Additionally, the researchers discovered an Economic Denial of Sustainability (EDoS), where the outgoing bandwidth of a vulnerable system is drained, raising the cost of operations if hosted by a third-party cloud service provider.
Impact
An adversary can abuse these security vulnerabilities to create one-way proxies and spoof source IPv4/6 addresses. Vulnerable systems may also allow access to an organization’s private network or be abused to perform DDoS attacks.
Solution
See the “Defences” section in the researcher’s publication https://papers.mathyvanhoef.com/usenix2025-tunnels.pdf
Acknowledgements
Thanks to the researchers Mathy Vanhoef and Angelos Beitis of the DistriNet-KU Leuven research group for the initial discovery and research. This document was written by Ben Koo.
CVE-2024-7595
GRE and GRE6 Protocols (RFC2784) do not validate or verify the source of a network packet, allowing an attacker to route arbitrary traffic via an exposed network interface that can lead to spoofing, access control bypass, and other unexpected network behaviors. This can be considered similar to CVE-2020-10136.
CVE-2024-7596
Proposed Generic UDP Encapsulation (GUE) (IETF draft-ietf-intarea-gue*) does not validate or verify the source of a network packet, allowing an attacker to route arbitrary traffic via an exposed network interface that can lead to spoofing, access control bypass, and other unexpected network behaviors. This can be considered similar to CVE-2020-10136.
*Note: GUE Draft is expired and no longer canonical.
CVE-2025-23018
The IPv4-in-IPv6 and IPv6-in-IPv6 protocols (RFC2473) do not require the validation or verification of the source of a network packet, allowing an attacker to route arbitrary traffic via an exposed network interface that can lead to spoofing, access control bypass, and other unexpected network behaviors. This can be considered similar to CVE-2020-10136.
CVE-2025-23019
The IPv6-in-IPv4 protocol (RFC4213) does not require authentication of incoming packets, allowing an attacker to route traffic via an exposed network interface that can lead to spoofing, access control bypass, and other unexpected network behaviors.
Note: CVE-2024-7595, CVE-2024-7596, and CVE-2025-23018 are considered similar to CVE-2020-10136 in that they highlight the inherent weakness that these protocols do not validate or verify the source of a network packet. These distinct CVEs are meant to specify the different protocols in question that are vulnerable.
For reference: (CVE-2020-10136) Multiple products that implement the IP Encapsulation within IP (IPIP) standard (RFC 2003, STD 1) decapsulate and route IP-in-IP traffic without any validation, which could allow an unauthenticated remote attacker to route arbitrary traffic via an exposed network interface and lead to spoofing, access control bypass, and other unexpected network behaviors.

Overview
Rsync, a versatile file-synchronizing tool, contains six vulnerabilities present within versions 3.3.0 and below. Rsync can be used to sync files between remote and local computers, as well as storage devices. The discovered vulnerabilities include heap-buffer overflow, information leak, file leak, external directory file-write,–safe-links bypass, and symbolic-link race condition.
Description
Many backup programs, such as Rclone, DeltaCopy, and ChronoSync use Rsync as backend software for file synchronization. Rsync can also be used in Daemon mode and is widely used in in public mirrors to synchronize and distribute files efficiently across multiple servers.
Following are the discovered vulnerabilities:
CVE-2024-12084 A heap-buffer-overflow vulnerability in the Rsync daemon results in improper handling of attacker-controlled checksum lengths (s2length). When the MAX_DIGEST_LEN exceeds the fixed SUM_LENGTH (16 bytes), an attacker can write out-of-bounds in the sum2 buffer.
CVE-2024-12085 When Rsync compares file checksums, a vulnerability in the Rsync daemon can be triggered. An attacker could manipulate the checksum length (s2length) to force a comparison between the checksum and uninitialized memory and leak one byte of uninitialized stack data at a time.
CVE-2024-12086 A vulnerability in the Rsync daemon could cause a server to leak the contents of arbitrary files from clients’ machines. This happens when files are copied from client to server. During the process, a malicious Rsync server can generate invalid communication tokens and checksums from data the attacker compares. The comparison will trigger the client to ask the server to resend data, which the server can use to guess a checksum. The server could then reprocess data, byte to byte, to determine the contents of the target file.
CVE-2024-12087 A path traversal vulnerability in the Rsync daemon affects the –inc-recursive option, a default-enabled option for many flags that can be enabled by the server even if not explicitly enabled by the client. When using this option, a lack of proper symlink verification coupled with de-duplication checks occurring on a per-file-list basis could allow a server to write files outside of the client’s intended destination directory. A malicious server could remotely trigger this activity by exploiting symbolic links named after valid client directories/paths.
CVE-2024-12088 A –safe-links option vulnerability results in Rsync failing to properly verify whether the symbolic link destination contains another symbolic link within it. This results in a path traversal vulnerability, which may lead to arbitrary files being written outside of the desired directory.
CVE-2024-12747 Rsync is vulnerable to a symbolic-link race condition, which may lead to privilege escalation. A user could gain access to privileged files on affected servers.
Impact
When combined, the first two vulnerabilities (heap buffer overflow and information leak) allow a client to execute arbitrary code on a device that has an Rsync server running. The client requires only anonymous read-access to the server, such as public mirrors.
Additionally, attackers can take control of a malicious server and read/write arbitrary files of any connected client. Sensitive data, such as SSH keys, can be extracted, and malicious code can be executed by overwriting files such as ~/.bashrc or ~/.popt.
Solution
Apply the latest patches available at https://github.com/RsyncProject/rsync and https://download.samba.org/pub/rsync/src/. Users should run updates on their software as soon as possible. As Rsync can be distributed bundled, ensure any software that provides such updates is also kept current to address these vulnerabilities.
Acknowledgements
Thanks to Simon Scannell, Pedro Gallegos, and Jasiel Spelman at Google Cloud Vulnerability Research for discovering the first five vulnerabilities; thanks to Aleksei Gorban for discovering the symbolic-link race condition. Finally, thanks to Andrew Tridgell for reporting all of them.
This document was written by Dr. Elke Drennan, CISSP.

Overview
The Howyar UEFI Application “Reloader” (32-bit and 64-bit), distributed as part of SysReturn prior to version 10.2.02320240919, is vulnerable to the execution of arbitrary software from a hard-coded path. An attacker who successfully exploits this vulnerability can bypass the UEFI Secure Boot feature and execute unsigned code during the boot process in the UEFI context.
Description
The Unified Extensible Firmware Interface (UEFI) is a specification for firmware architecture that facilitates interaction between a computing platform’s hardware and operating system during the early boot phase. When a UEFI-compliant computer is powered on, the UEFI implementation (including multiple UEFI applications) is the first software to run, preceding the operating system. UEFI applications are typically digitally signed, often by the Microsoft UEFI Certificate Authority (CA), ensuring their trusted execution under UEFI Secure Boot. UEFI bootloaders, a type of UEFI application, provide early boot management, loading OS files into protected memory areas for execution. These bootloaders can execute additional software and load drivers as part of their startup processes.
The Howyar Reloader UEFI application, an UEFI bootloader available in both 32-bit and 64-bit versions, has been found to contain an arbitrary code execution vulnerability. Researchers at ESET discovered that the application allows execution of UEFI software from a hard-coded path without verifying its signature. This occurs because the Reloader does not use UEFI’s standard BootServices LoadImage() API for safe application execution. Consequently, any unsigned third-party software can be executed during the early boot phase with high privileges in the UEFI context. Since the Reloader application is signed by the trusted Microsoft UEFI CA, it can be installed on any UEFI-compliant system. Furthermore, as it is bundled and distributed as part of supply-chain software, it may also be present in other UEFI implementations provided by software suppliers or OEMs.
An attacker with the ability to update the UEFI bootloader can exploit this vulnerability to run arbitrary code, bypassing UEFI Secure Boot. On systems where a vulnerable version of the Reloader application is present, an attacker only needs to install a malicious unsigned UEFI application in a hard-coded path to achieve Secure Boot bypass and execute code in the UEFI context.
To mitigate this vulnerability, updated Reloader should be installed on the affected systesm. It is also essential that all UEFI compliant computers also update their Secure Boot Forbidden Signature Database (DBX or Revocation List), supplied by the UEFI Forum. This update should be applied to the special SPI flash memory on the motherboard, which stores firmware data. Maintaining the integrity of the UEFI Secure Boot ecosystem requires the timely application of these updates.
Impact
An attacker can bypass Secure Boot at system startup and execute arbitrary code before the operating system (OS) loads. Code executed in this early boot phase can persist on the system, potentially loading malicious kernel extensions that survive both reboots and OS reinstallation. Additionally, it may evade detection by OS-based and endpoint detection and response (EDR) security measures.
Solution
Apply a Patch
Howyar Technologies and their partners have released updated software to address this vulnerability. Please follow their guidance to install the updated version of the software. Additionally, Microsoft has indicated that they intend to provide an updated DBX (Revocation List) file around January 14, 2025. These updates may also be delivered by your OEM or OS vendor to ensure the Secure Boot Forbidden Signature Database (DBX) is up to date.
Recommendations for Enterprises and Developers
As changes to the DBX file can lead to system instability, vendors are urged to thoroughly test the updates to ensure they do not render systems unusable. Enterprises and cloud providers managing large numbers of systems should prioritize applying these updates and ensure the DBX file changes are implemented reliably to prevent loading of unsigned binaries in the virtual machine boot process.
Acknowledgements
Thanks to Martin Smolar of ESET for his responsible disclosure of this vulnerability to Howyar Technologies and other affected vendors. Thanks also to Howyar Technologies that closely worked with the researcher and CERT/CC to resolve this vulnerability. This document was written by Vijay Sarvepalli.

Overview
PDQ Deploy is a service intended for usage by system administrators for the deployment of software or updates to targeted machines within their network. PDQ Deploy uses “run modes” to deploy software to their target devices. The run mode “Deploy User” insecurely creates credentials on the target device. These credentials are deleted from the device following a full deployment of a software file, however, an attacker with access to the target device can compromise these credentials prior to deletion through common password tools such as Mimikatz. These credentials could then be used to gain administrator access on the target device, or to compromise any other device using these credentials that is enrolled through active directory and has previously had software deployed to it by PDQ Deploy.
Description
PDQ Deploy is a service intended for usage by system administrators and others for the deployment of software or updates to targeted machines within their network. PDQ Deploy has various configurations, including automated deployment and availability based deployments. PDQ Deploy also uses various “run modes” to deploy software to their target devices. The “Deploy User” run mode can use a domain or local account with administrator rights on the target computer during the deployment process.
The deployment process is as follows:
1: PDQ Deploy initiates an application deployment.
2: The central server connects to the target device remotely with the “Deploy User” credentials.
3: A local service is created on the device and is run as the selected domain or local user account specified as the deploy user.
4: PDQ follows the application deployment process, installing the requested software.
5: The service is removed from the remote device.
An attacker with access to the device can use a password dumping tool, such as Mimikatz, to dump these credentials during the deployment process, specifically during steps 2 to 4, prior to their deletion. If using a domain user, these credentials created by the Deploy User domain account are static and can be used to compromise any other device that is enrolled in PDQ Deploy through Active Directory sharing this user, allowing for lateral movement.
PDQ Deploy supports other “Run Modes” for use during the deployment process. These run modes alter how credentials are saved on the device. These include the “Local System” deploy mode, in which the service is ran as a Local System account. A Local System account has lower privileges than a domain account, but PDQ Deploy still uses the Deploy User Account to connect to the device and initiate the Local System account, resulting in the vulnerabilities still being present for that user.
Impact
An attacker with access to the PDQ Deploy service and the ability to execute common password tools such as Mimikatz can dump the Deploy User administrator credentials from a device during the deployment process, then use those credentials to either further compromise the current device, or move laterally and compromise other PDQ Deploy enrolled systems on the Active Directory system that share the user and use a domain account. The compromised machine must have been previously deployed to via PDQ Deploy.
Solution
The CERT/CC is creating this Vulnerability Note to advise and make users of PDQ Deploy aware of potential avenues of attack through the deploy service. System administrators that are using PDQ Deploy should employ LAPS to mitigate this vulnerability. System administrators could also follow the recommendations outlined in the How-to-Guides listed on the PDQ Deploy website. (https://help.pdq.com/hc/en-us/articles/360033877651-Adding-and-Using-Multiple-Credentials-in-PDQ-Deploy-Inventory) Additionally, alternate deploy modes could be used. The “Logged on User” deploy mode utilizes the active credentials of the device currently logged in to create the necessary services and deploy the requested software.This deploy mode does not create a service with the domain/local credentials, and as such, is an appropriate deployment mode to avoid the vulnerability. It should be noted this Run Mode is only available on the Enterprise mode, and requires user input to complete the deployment of the software.
Acknowledgements
Thanks to the reporter who wishes to remain anonymous. A French source validated and coordinated this vulnerability note and case with CERT/CC. This document was written by Christopher Cullen.