CVE-2015-4000: TLS DHE_EXPORT cipher downgrade enables Logjam man-in-the-middle attacks

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 17 September 2026. Confidence: high.

medium priorityThe CVSS score is low and no KEV listing exists, but the very high EPSS and broad vendor exposure make it worth remediating, especially on internet-facing TLS services.

What it is

TLS 1.2 and earlier mishandles the DHE_EXPORT ciphersuite when a server enables it but the client does not, allowing a man-in-the-middle to rewrite the ClientHello to force DHE_EXPORT and then rewrite the ServerHello back to DHE. This is the Logjam issue, which lets an attacker downgrade the key exchange to weak export-grade Diffie-Hellman parameters. It matters because it undermines the confidentiality of TLS sessions that should have used strong ephemeral key exchange.

Impact

An attacker positioned in the network path can downgrade the TLS handshake to export-grade DHE and then recover or weaken the session key, exposing encrypted traffic. The CVSS vector rates only low integrity impact with no confidentiality or availability impact, so the practical gain is limited to breaking the negotiated key exchange rather than direct code execution.

Attack surface

Reachable over the network by a man-in-the-middle who can intercept and modify TLS handshake messages between client and server. No authentication or user interaction is required, but the attack depends on the server offering a DHE_EXPORT ciphersuite that the client did not request.

Exploitation

CISA KEV does not list this CVE, but EPSS is extremely high at 0.9986 (99.96th percentile), indicating strong predicted exploitation activity. Reference tags are only Third Party Advisory and Mailing List, with no public exploit or in-the-wild tag supplied.

What to do

• Patch affected TLS stacks and products to versions that remove or disable DHE_EXPORT ciphersuites, prioritizing OpenSSL and the listed vendor platforms.
• Disable all export-grade and DHE_EXPORT cipher suites in server and client TLS configurations.
• Use Diffie-Hellman parameters of at least 2048 bits and reject handshakes that negotiate export-grade groups.
• Enforce TLS 1.2 or later with modern cipher suites and disable legacy protocol fallback where possible.
• Review network paths for interception exposure and apply certificate pinning or authenticated key exchange where feasible.

Detection

• Monitor TLS handshake logs for DHE_EXPORT or other export-grade cipher suites being negotiated.
• Alert on repeated ClientHello or ServerHello rewrites or unexpected cipher suite changes in network traffic inspection.
• Scan internal and external TLS endpoints for support of export-grade Diffie-Hellman ciphersuites.
• Correlate IDS/IPS signatures for Logjam-style downgrade attempts with TLS session metadata.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.