CVE-2023-6937

Improper (D)TLS key boundary enforcement

MEDIUM
5.3
CVSS Score
Published: February 15, 2024 at 05:21 PM UTC
Updated: June 17, 2026 at 06:51 AM UTC
1 product affected across 1 vendorwolfSSL

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Severity
MEDIUM5.3
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

Description

wolfSSL prior to 5.6.6 did not check that messages in one (D)TLS record do not span key boundaries. As a result, it was possible to combine (D)TLS messages using different keys into one (D)TLS record. The most extreme edge case is that, in (D)TLS 1.3, it was possible that an unencrypted (D)TLS 1.3 record from the server containing first a ServerHello message and then the rest of the first server flight would be accepted by a wolfSSL client. In (D)TLS 1.3 the handshake is encrypted after the ServerHello but a wolfSSL client would accept an unencrypted flight from the server. This does not compromise key negotiation and authentication so it is assigned a low severity rating.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v ≤ 5.6.4v ≤ 5.64v < 5.6.6
Affected range stops below 5.6.6, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.3MEDIUMwolfSSL
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-20NVD-CWE-Other

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