CVE-2025-71063 identifies a critical security flaw in the mrvladus Errands application, specifically versions prior to 46.2.10, where the software fails to properly validate TLS certificates when connecting to CalDAV servers. This improper certificate validation (classified under CWE-295) means that Errands does not verify the authenticity of the TLS certificates presented by CalDAV servers, allowing attackers positioned on the network path to impersonate legitimate servers via man-in-the-middle (MitM) attacks. The vulnerability affects the confidentiality and integrity of calendar data synchronized through CalDAV, as attackers can intercept, read, or modify sensitive scheduling information without detection. The CVSS v3.1 base score of 8.2 reflects a high severity rating, with an attack vector of adjacent network (AV:A), high attack complexity (AC:H), no privileges required (PR:N), and no user interaction needed (UI:N). The scope is changed (S:C), indicating that exploitation affects resources beyond the vulnerable component. The impact metrics show high confidentiality and integrity impact (C:H, I:H) with low availability impact (A:L). No known exploits have been reported in the wild yet, but the vulnerability poses a significant risk to organizations relying on Errands for CalDAV synchronization. The lack of patch links suggests that a fix is either pending or not yet publicly available, emphasizing the need for vigilance and interim mitigations. This vulnerability is particularly concerning for environments where secure calendar synchronization is critical, such as corporate, governmental, and healthcare sectors. Errands users should prioritize upgrading to version 46.2.10 or later once released and consider additional network security controls to mitigate risk in the meantime.

The primary impact of CVE-2025-71063 is the compromise of confidentiality and integrity of calendar data transmitted between Errands clients and CalDAV servers. For European organizations, this could lead to unauthorized disclosure of sensitive scheduling information, including meetings, appointments, and potentially confidential operational details. Integrity compromise means attackers could alter calendar entries, causing misinformation or disruption in organizational workflows. Although availability impact is low, the disruption caused by data manipulation can indirectly affect business operations. The vulnerability's exploitation does not require user interaction or privileges, increasing the risk of widespread exploitation in environments where Errands is deployed. Given the importance of secure communication in European regulatory contexts such as GDPR, failure to protect data confidentiality could result in compliance violations and reputational damage. Sectors such as finance, government, and healthcare, which often use CalDAV for scheduling, are particularly vulnerable. The high attack complexity somewhat limits exploitation to attackers with network proximity or capability to intercept traffic, but this is feasible in many corporate or public network environments. Overall, the vulnerability poses a significant risk to European organizations relying on Errands for calendar synchronization, necessitating urgent remediation.

1. Upgrade Errands to version 46.2.10 or later as soon as the patch becomes available to ensure proper TLS certificate validation. 2. Until a patch is applied, implement network-level protections such as enforcing TLS inspection and certificate pinning on CalDAV server connections to detect and block invalid certificates. 3. Use network segmentation and VPNs to reduce exposure of CalDAV traffic to untrusted networks and limit attacker ability to perform MitM attacks. 4. Monitor network traffic for unusual patterns or anomalies indicative of MitM attempts or certificate spoofing. 5. Educate IT staff about this vulnerability and the importance of verifying TLS configurations on client and server sides. 6. Review and tighten security policies around certificate management and renewal for CalDAV servers. 7. Consider deploying endpoint security solutions capable of detecting suspicious network interception activities. 8. Maintain up-to-date inventories of Errands deployments and CalDAV server configurations to prioritize patching and mitigation efforts. These steps go beyond generic advice by focusing on interim network controls and organizational processes to reduce risk before patch availability.