Bug 1877557 (CVE-2020-12413)

Summary:	CVE-2020-12413 nss: Information exposure when DH secret are reused across multiple TLS connections
Product:	[Other] Security Response	Reporter:	Pedro Sampaio <psampaio>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED WONTFIX	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	cmoore, crypto-team, dchong, dueno, elio.maldonado.batiz, kai-engert-fedora, kaycoth, kdudka, nss-nspr-maint, rrelyea, sdarade, yozone
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:	A flaw was found in Mozilla nss. A raccoon attack exploits a flaw in the TLS specification which can lead to an attacker being able to compute the pre-master secret in connections which have used a Diffie-Hellman(DH) based ciphersuite. In such a case this would result in the attacker being able to eavesdrop on all encrypted communications sent over that TLS connection. The highest threat from this vulnerability is to data confidentiality.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-11-02 17:45:55 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:	1879367, 1877558, 1878921, 1878922, 1879366, 1910629
Bug Blocks:	1877559

Description Pedro Sampaio 2020-09-09 20:24:42 UTC

A flaw was found in Mozilla nss. Raccoon attack exploits a flaw in the TLS specification which can lead to an attacker being able to compute the pre-master secret in connections which have used a Diffie-Hellman (DH) based ciphersuite. In such a case this would result in the attacker being able to eavesdrop on all encrypted communications sent over that TLS connection. The highest threat from this vulnerability is to data confidentiality.

References:

https://raccoon-attack.com/

Comment 1 Pedro Sampaio 2020-09-09 20:25:03 UTC

Created nss tracking bugs for this issue:

Affects: fedora-all [bug 1877558]

Comment 3 Todd Cullum 2020-09-15 19:23:11 UTC

Statement:

NSS as shipped with Red Hat Enterprise Linux 6, 7, and 8 does not re-use Diffie-Hellman Ephemeral (DHE) keys. It reuses Elliptic Curve Diffie-Hellman Ephemeral (ECDHE) keys by default, but Attacking ECDH and ECDHE cipher suites are not in the scope of the Raccoon Attack and generally considered to be unaffected [1]. Further, reuse of ECDHE keys can be disabled starting in nss 3.17 [2].

For these reasons, Red Hat Product Security has marked the Severity of this flaw as Low. Please see [3] for more information about Low Severity ratings.

1. https://raccoon-attack.com/RacoonAttack.pdf pg. 13
2. https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/NSS_3.17_release_notes
3. https://access.redhat.com/security/updates/classification

Comment 4 Todd Cullum 2020-09-15 19:26:22 UTC

External References:

Thorough Explanation can be found: https://raccoon-attack.com/RacoonAttack.pdf
Raccoon Attack: Finding and Exploiting Most-Significant-Bit-Oracles in TLS-DH(E) by Robert Merget, Marcus Brinkmann, et al.

Comment 5 Todd Cullum 2020-09-15 19:31:41 UTC

Mitigation:

Any risk involving ECDHE key reuse on the nss server can be mitigated by setting the SSL_REUSE_SERVER_ECDHE_KEY socket option to PR_FALSE.