CVE-2023-6937: wolfssl Input Validation Flaw — Fix

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.

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CVSS v3.1 Score

5.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Weakness Type (CWE)

CWE-20 Improper Input Validation

Affected Products

Vendor	Product	Versions
wolfssl	wolfssl	< 5.6.6

References

Advisories & Patches

https://github.com/wolfSSL/wolfssl/pull/7029 https://www.wolfssl.com/docs/security-vulnerabilities/ https://github.com/wolfSSL/wolfssl/pull/7029 https://www.wolfssl.com/docs/security-vulnerabilities/

Frequently Asked Questions

What is CVE-2023-6937? +

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. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2023-6937? +

CVE-2023-6937 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2023-6937? +

CVE-2023-6937 affects products from wolfssl, specifically: wolfssl. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2023-6937? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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