CVE-2026-5773: SMB Connection Reuse in libcurl

The primary impact of CVE-2026-5773 is the potential for unintended data retrieval. An attacker could craft a malicious SMB(S) request that exploits this connection reuse error, causing an application using libcurl to download a file different from what was intended. This could lead to data corruption, unauthorized access to sensitive information, or even the execution of malicious code if the downloaded file is an executable. The blast radius depends on the application using libcurl; a widely used application could expose a large number of systems to this risk. While not directly exploitable for remote code execution, the misdirection of file downloads presents a significant operational and security concern.

1. Gereserveerd2026-04-08
2. Gepubliceerd2026-05-13
3. EPSS bijgewerkt2026-05-13

The recommended mitigation for CVE-2026-5773 is to upgrade to libcurl version 8.19.1 or later. If an immediate upgrade is not feasible due to compatibility issues or system downtime constraints, consider implementing temporary workarounds. These might involve disabling SMB(S) connection reuse within the application (if possible) or carefully validating the file paths and shares used in SMB(S) transfers. Network firewalls and intrusion detection systems should be configured to monitor for unusual SMB(S) traffic patterns. After upgrading, confirm the fix by performing a test SMB(S) transfer and verifying that the correct file is downloaded.