CWE-757: Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')

BaseIncomplete

A protocol or its implementation supports interaction between multiple actors and allows those actors to negotiate which algorithm should be used as a protection mechanism such as encryption or authentication, but it does not select the strongest algorithm that is available to both parties.

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Extended Description

When a security mechanism can be forced to downgrade to use a less secure algorithm, this can make it easier for attackers to compromise the product by exploiting weaker algorithm. The victim might not be aware that the less secure algorithm is being used. For example, if an attacker can force a communications channel to use cleartext instead of strongly-encrypted data, then the attacker could read the channel by sniffing, instead of going through extra effort of trying to decrypt the data using brute force techniques.

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Detect Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade') with Automated Static Analysis

Documented detection approaches include Automated Static Analysis; recorded impacts include Bypass Protection Mechanism; the entry maps to CAPEC-220, CAPEC-606, and CAPEC-620. Use these source-defined anchors to turn CWE-757 into implementation, review, and verification checks for the affected component.

CWE-757: Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade') — MITRE CWE

Prevent CWE-757 through an SSDF control plan

Use NIST SSDF practices to make prevention of CWE-757, Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade'), an explicit development outcome. Translate the CWE definition into security requirements and design constraints, choose safer implementation patterns and toolchain checks, and define acceptance evidence before release. Feed every confirmed occurrence back into the requirements, design review, and coding rules so the same root cause is removed across the product rather than patched in one location.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Triage CWE-757 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-757, Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade'), has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-757

Apply MITRE's full root-cause mapping guidance when using CWE-757, Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade'). Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-757 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-757, Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade'). Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-757: Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')?+

CWE-757: Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade') is a Common Weakness Enumeration (CWE) entry maintained by MITRE. A protocol or its implementation supports interaction between multiple actors and allows those actors to negotiate which algorithm should be used as a protection mechanism such as encryption or authentication, but it does not select the strongest algorithm that is available to both parties. When a security mechanism can be forced to downgrade to use a less secure algorithm, this can make it easier for attackers to compromise the product by exploiting weaker algorithm. The victim might not be aware that the less secure algorithm is being used. For example, if an attacker can force a communications channel to use cleartext instead of strongly-encrypted data, then the attacker could read the channel by sniffing, instead of going through extra effort of trying to decrypt the data using brute force techniques.

What are the security consequences of Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')?+

If exploited, CWE-757 (Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')) it can compromise Access Control, leading to outcomes such as Bypass Protection Mechanism.

Which programming languages are affected by Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')?+

CWE-757 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What are real-world examples of Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')?+

MITRE documents real CVEs mapped to CWE-757, including CVE-2006-4302, CVE-2006-4407, CVE-2005-2969, CVE-2001-1444 and CVE-2002-1646. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-757 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

CWE-757: Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')

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Observed CVE Examples (5)

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