Security readout for executives and security teams
Plain-English summary
CVE-2015-1637 is Microsoft’s Schannel exposure to the FREAK TLS downgrade issue. An attacker able to interfere with TLS traffic could make some connections use weak export-grade RSA cryptography, reducing confidentiality. The issue affects multiple older Windows client and server versions listed by Microsoft.
Executive priority
Treat as a legacy TLS weakness requiring cleanup, not an emergency based on current evidence. Prioritize patch confirmation on exposed Windows systems and remove obsolete cryptography from TLS configurations.
Technical view
Schannel did not properly restrict TLS state transitions, enabling remote attackers to conduct cipher-downgrade attacks to EXPORT_RSA ciphers using crafted TLS traffic. Microsoft tracks the fix in MS15-031 and security update 3046015. This is related to FREAK but distinct from CVE-2015-0204 and CVE-2015-1067.
Likely exposure
Exposure is most likely on affected Windows systems using Schannel for TLS, especially internet-facing services or clients that negotiate with untrusted servers. The source bundle names Windows Server 2003 SP2 through Windows 8.1, Server 2012 R2, and Windows RT versions.
Exploitation context
The bundle supports remote downgrade risk but does not cite confirmed active exploitation. CISA KEV status is false. Practical exploitation generally depends on attacker network position, vulnerable TLS negotiation, and availability of export-grade RSA cipher paths.
Researcher notes
The public record lacks CVSS and CWE details in the bundle. Analysis should distinguish this Schannel TLS state-transition flaw from related FREAK CVEs affecting other implementations. Do not assume exploit prevalence without additional evidence.
Mitigation direction
- Apply Microsoft MS15-031 / security update 3046015 where applicable.
- Check Microsoft guidance for affected or legacy Windows versions.
- Disable export-grade RSA cipher suites where supported.
- Prioritize internet-facing systems that use Windows Schannel for TLS.
- Plan remediation or isolation for systems that cannot receive the update.
Validation and detection
- Inventory Windows hosts matching the Microsoft affected-version list.
- Confirm MS15-031 / update 3046015 is installed where applicable.
- Review TLS configuration for negotiable EXPORT_RSA cipher suites.
- Check externally exposed TLS endpoints using Schannel.
- Document exceptions where systems cannot be patched.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CVE-2015-1637 mapping review
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Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://technet.microsoft.com/library/security/3046015CVE reference · x_refsource_CONFIRM
- https://freakattack.com/CVE reference · x_refsource_MISC
- MS15-031CVE reference · vendor-advisory, x_refsource_MS
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.