TLS Protocol up to 1.2 DHE_EXPORT Ciphersuite Logjam cryptographic issues

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CTI Interest Score
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A vulnerability has been found in TLS Protocol up to 1.2 and classified as critical. This vulnerability affects an unknown functionality of the component DHE_EXPORT Ciphersuite. The manipulation with an unknown input leads to a weak encryption vulnerability (Logjam). The CWE definition for the vulnerability is CWE-310. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

The TLS protocol 1.2 and earlier, when a DHE_EXPORT ciphersuite is enabled on a server but not on a client, does not properly convey a DHE_EXPORT choice, which allows man-in-the-middle attackers to conduct cipher-downgrade attacks by rewriting a ClientHello with DHE replaced by DHE_EXPORT and then rewriting a ServerHello with DHE_EXPORT replaced by DHE, aka the "Logjam" issue.

The weakness was released 05/21/2015 by David Adrian, Karthikeyan Bhargavan, Zakir Durumeric, Pierrick Gaudry, Matthew Green, J. Alex Halderman, Nadia Heninger, Drew Springall, Emmanuel Thomé, Luke Valenta, Benjamin VanderSloot, Eric Wustrow, Santiago Zanella-Béguelink and Paul Zimmermann as FG-IR-15-013 / CTX201114 as confirmed mailinglist post (oss-sec). The advisory is shared for download at This vulnerability was named CVE-2015-4000 since 05/15/2015. The exploitation appears to be difficult. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $5k-$25k (estimation calculated on 05/03/2019). The MITRE ATT&CK project declares the attack technique as T1600. This vulnerability has a historic impact due to its background and reception.

As 0-day the estimated underground price was around $25k-$100k. The vulnerability scanner Nessus provides a plugin with the ID 83937 (Fedora 21 : nss-3.19.1-1.0.fc21 / nss-softokn-3.19.1-1.0.fc21 / nss-util-3.19.1-1.0.fc21 (2015-9130) (Logjam)), which helps to determine the existence of the flaw in a target environment. It is assigned to the family Fedora Local Security Checks and running in the context local. The Nessus plugin is testing the existence of the vulnerability with the following NASL code:

if (rpm_check(release:"ALA", reference:"openssl-1.0.1k-10.86.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"openssl-debuginfo-1.0.1k-10.86.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"openssl-devel-1.0.1k-10.86.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"openssl-perl-1.0.1k-10.86.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"openssl-static-1.0.1k-10.86.amzn1")) flag++;

if (flag)
  if (report_verbosity > 0) security_hole(port:0, extra:rpm_report_get());
  else security_hole(0);
The commercial vulnerability scanner Qualys is able to test this issue with plugin 350152 (Amazon Linux Security Advisory for openssl: ALAS-2015-550).

It is possible to mitigate the problem by applying the configuration setting . A possible mitigation has been published 2 weeks after the disclosure of the vulnerability. The mailinglist post contains the following remark:

We have three recommendations for correctly deploying Diffie-Hellman for TLS: 1. Disable Export Cipher Suites, 2. Deploy (Ephemeral) Elliptic-Curve Diffie-Hellman (ECDHE), 3. Generate a Strong, Unique Diffie Hellman Group.
Furthermore it is possible to detect and prevent this kind of attack with TippingPoint and the filter 19886.

The vulnerability is also documented in the databases at SecurityFocus (BID 74733), X-Force (103294), Vulnerability Center (SBV-51701) and Tenable (83937). Additional details are provided at Entries connected to this vulnerability are available at 75951, 78627, 78668 and 80581.


  • Debian GNU/Linux



CPE 2.3infoedit

CPE 2.2infoedit




VulDB Meta Base Score: 3.7
VulDB Meta Temp Score: 3.3

VulDB Base Score: 3.7
VulDB Temp Score: 3.3
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NVD Base Score: 3.7
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Name: Logjam
Class: Weak encryption / Logjam
CWE: CWE-310
ATT&CK: T1600

Local: No
Remote: Yes

Availability: 🔍
Status: Unproven

Price Prediction: 🔍
Current Price Estimation: 🔍


Nessus ID: 83937
Nessus Name: Fedora 21 : nss-3.19.1-1.0.fc21 / nss-softokn-3.19.1-1.0.fc21 / nss-util-3.19.1-1.0.fc21 (2015-9130) (Logjam)
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OpenVAS ID: 14611
OpenVAS Name: Amazon Linux Local Check: alas-2015-586
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Threat Intelligenceinfoedit

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Recommended: Config
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05/15/2015 🔍
05/19/2015 +4 days 🔍
05/20/2015 +1 days 🔍
05/21/2015 +1 days 🔍
05/21/2015 +0 days 🔍
05/30/2015 +9 days 🔍
06/02/2015 +3 days 🔍
07/08/2015 +36 days 🔍
08/02/2015 +25 days 🔍
01/08/2019 +1255 days 🔍
05/03/2019 +115 days 🔍


Advisory: FG-IR-15-013 / CTX201114
Researcher: David Adrian/Karthikeyan Bhargavan/Zakir Durumeric/Pierrick Gaudry/Matthew Green/J. Alex Halderman/Nadia Heninger/Drew Springall/Emmanuel Thomé/Luke Valenta/Benjamin VanderSloot/Eric Wustrow/Santiago Zanella-Béguelink/Paul Zimmermann
Status: Confirmed
Confirmation: 🔍

CVE: CVE-2015-4000 (🔍)

SecurityFocus: 74733 - SSL/TLS LogJam Man in the Middle Security Bypass Vulnerability
X-Force: 103294 - TLS Diffie-Hellman Key Exchange information disclosure
Vulnerability Center: 51701 - TLS <=1.2 Remote Man-in-the Middle via Cipher-Downgrade Attacks (aka \, Medium
OSVDB: 122331

Misc.: 🔍
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Created: 05/21/2015 10:17 AM
Updated: 05/03/2019 09:38 PM
Changes: (15) vulnerability_cvss3_vuldb_av vulnerability_cvss3_vuldb_ac vulnerability_cvss3_vuldb_pr vulnerability_cvss3_vuldb_ui vulnerability_cvss3_vuldb_s vulnerability_cvss3_vuldb_c vulnerability_cvss3_vuldb_i vulnerability_cvss3_vuldb_a countermeasure_date source_openvas_id source_openvas_filename source_openvas_title source_openvas_family source_mcafee_ips_id source_mcafee_ips_version
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