Bug 2506857 (CVE-2026-66032)

Summary:	CVE-2026-66032 libssh2: libssh2: Arbitrary code execution via double-free in SFTP session
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	kshier, profitable.scorpion.bfxw, rhel-process-autobot, stcannon, teagle, watson-tool-maintainers, yguenane
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in libssh2. A malicious SSH (Secure Shell) server can exploit a double-free vulnerability in the sftp_open() function. This flaw allows the server to corrupt the heap memory of an authenticated client when it opens an SFTP (SSH File Transfer Protocol) session. This heap corruption can lead to arbitrary code execution on the client system, giving the attacker control over the affected system.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2507359, 2507360, 2507361
Bug Blocks:

Description OSIDB Bzimport 2026-07-24 17:03:46 UTC

libssh2 through 1.11.1, fixed in commit 5e47761, contains a double-free vulnerability in the sftp_open() function in src/sftp.c that allows a malicious SSH server to corrupt the heap of any authenticated client opening an SFTP session. When a server responds to SSH_FXP_OPEN with SSH_FXP_STATUS containing FX_OK, the response data buffer is freed, and if a subsequent sftp_packet_require() call returns a specific error such as LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED, the same pointer is freed a second time, enabling tcache dup conditions on glibc systems that allow overlapping allocations and function pointer overwrites.

Comment 2 Matt Cowell 2026-08-11 09:01:08 UTC

I have seen this bug on a website I manage ( https://basketballbrosgame.org ). I’ve checked the affected libssh2 package and tried updating it to the latest available version, but I’m still seeing the SFTP problem. I’m not sure yet whether the website itself is directly affected or if it’s coming from the system package.

Comment 3 errata-xmlrpc 2026-08-31 17:34:20 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7 Extended Lifecycle Support

Via RHSA-2026:61752 https://access.redhat.com/errata/RHSA-2026:61752