What’s Vulnerable › Vulnerabilities

CVE-2026-5773: wrong reuse of SMB connection

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-05-13 · updated 2026-09-15
• Weakness: CWE-488

Description

libcurl might in some circumstances reuse the wrong connection for SMB(S) transfers. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of criteria must be met. Due to a logical error in the code, a network transfer operation that was requested by an application could wrongfully reuse an existing SMB connection to the same server that was using a different "share" than the new subsequent transfer should. This could in unlucky situations lead to the download of the wrong file or the upload of a file to the wrong place. When this happens, the same credentials are used and the server name is the same.

Affected products

• curl: from 7.40.0 before 8.20.0 — fixed in 8.20.0

How to fix

Upgrade to a fixed version: curl 8.20.0. Check the vendor advisory for mitigations.

References

• https://curl.se/docs/CVE-2026-5773.html
• https://curl.se/docs/CVE-2026-5773.json
• https://hackerone.com/reports/3650689
• http://www.openwall.com/lists/oss-security/2026/04/29/9
• https://hackerone.com/reports/3650689

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