CVE-2026-5773

Publication date 29 April 2026

Last updated 22 May 2026

Ubuntu priority

Cvss 3 Severity Score

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.

Read the notes from the security team

Why is this CVE low priority?

curl is dropping support for SMB later in 2026 and only supports SMB version 1

Learn more about Ubuntu priority

Mitigation

Avoid using SMB

Status

Show unmaintained releases

Package	Ubuntu Release	Status
curl	26.04 LTS resolute	Fixed 8.18.0-1ubuntu2.1
	25.10 questing	Fixed 8.14.1-2ubuntu1.3
	24.04 LTS noble	Fixed 8.5.0-2ubuntu10.9
	22.04 LTS jammy	Fixed 7.81.0-1ubuntu1.24
	20.04 LTS focal	Vulnerable
	18.04 LTS bionic	Vulnerable
	16.04 LTS xenial	Vulnerable
	14.04 LTS trusty	Not affected

Notes

ebarretto

Introduced-in: https://github.com/curl/curl/commit/aec2e865f0

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
curl	Upstream: 74a1695

Severity score breakdown

Parameter	Value
Base score	7.5 · High
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	None
Scope	Unchanged
Confidentiality	High
Integrity impact	None
Availability impact	None
Vector	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

References

Related Ubuntu Security Notices (USN)

USN-8227-1
curl vulnerabilities
4 May 2026