Bug 1843707 (CVE-2020-10761)

Summary:	CVE-2020-10761 QEMU: nbd: reachable assertion failure in nbd_negotiate_send_rep_verr via remote client
Product:	[Other] Security Response	Reporter:	Pedro Sampaio <psampaio>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	amit, berrange, cfergeau, dwmw2, itamar, jen, jferlan, jforbes, jjoyce, jlyle, jmaloy, jschluet, knoel, lhh, lpeer, m.a.young, mburns, mkenneth, mrezanin, mst, pbonzini, ribarry, rjones, robinlee.sysu, sclewis, security-response-team, slinaber, virt-maint, virt-maint
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	QEMU 5.0.1	Doc Type:	If docs needed, set a value
Doc Text:	An assertion failure issue was found in the Network Block Device(NBD) Server of the QEMU. This flaw occurs when an nbd-client sends a spec-compliant request that is near the boundary of maximum permitted request length. A remote nbd-client could use this flaw to crash the qemu-nbd server resulting in a denial of service.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-12-15 12:03:21 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1845381, 1845384, 1845385, 1910688
Bug Blocks:	1843709

Description Pedro Sampaio 2020-06-03 21:41:21 UTC

Quick Emulator(Qemu) built with the Network Block Device(NBD) Server support is vulnerable to a crash via assertion failure. A nbd-client can cause denial of service by aborting QEMU as NBD server with a spec-compliant request that is near the boundary of maximum length permitted. A remote user/process could use this flaw to crash the qemu-nbd server resulting in DoS.

Upstream patch:
---------------
  -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg02031.html

Issue introduced since QEMU v4.2
  -> https://git.qemu.org/?p=qemu.git;a=commit;h=93676c88d7a5cd5971de94f9091eff8e9773b1af
  - It allowed nbd-client to send longer export names

Comment 2 Prasad Pandit 2020-06-09 05:20:09 UTC

Acknowledgments:

Name: Eric Blake (redhat.com), Xueqiang Wei (redhat.com)

Comment 3 Prasad Pandit 2020-06-09 05:20:31 UTC

Created qemu tracking bugs for this issue:

Affects: fedora-all [bug 1845381]

Comment 5 Prasad Pandit 2020-06-09 05:32:52 UTC

External References:

https://www.openwall.com/lists/oss-security/2020/06/09/1