Bug 2543853 (CVE-2026-94029)

Summary:	CVE-2026-94029 org.apache.sshd/sshd-sftp: Apache MINA SSHD: Denial of Service via memory exhaustion in SFTP check-file extension
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	ewittman, fmariani, fmongiar, gbenhaim, gmalinko, janstey, jnethert, jwon, mcarlett, nipatil, niyer, pantinor, pdelbell, pjindal, rkubis, rstepani, tcunning, twaugh, yfang
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in Apache MINA SSHD. When processing SSH File Transfer Protocol (SFTP) check-file extensions, the server accumulates file hash verification responses entirely in memory without enforcing a size limit. An authenticated remote attacker can exploit this vulnerability by requesting file verification with a minimal block size on a large file, leading to memory exhaustion and a Denial of Service (DoS).	Story Points:	---
Clone Of:		Environment:
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Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-09-30 09:47:14 UTC

Server-side memory exhaustion in Apache MINA SSHD 1.0.0 to 2.19.0 and 3.0.0-M1 to 3.0.0-M5, component sshd-sftp, in the SFTP v6 check-file-name/check-file-handle extension. Apache MINA SSHD is a Java library for client-side and server-side SSH.




Using a very small "block size" (for instance 256, which is the minimum) on a huge file generates many (file size / block size) hashes. The resulting SFTP reply message was accumulated fully in memory server-side, which could, with a suitably large (possibly sparse) file exhaust the server-side memory, taking down the server.




Users are recommended to upgrade to version 2.20.0 or 3.0.0-M6, which fix this issue by imposing a maximum limit on the size of the reply. Many SFTP implementations have a general limit on the size of SFTP messages anyway; typically 256kB as in OpenSSH or also in Apache MINA SSHD.