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5.3
CVE-2023-6937: wolfSSL before 5.6.6 may accept mixed key data
CVE-2023-6937 · published 2 years ago
Summary
Versions of wolfSSL older than 5.6.6 could combine data protected by different encryption keys into a single communication packet. In rare cases this might let a client accept an unencrypted part of a handshake that should have been encrypted, though it does not break authentication or key exchange. Upgrade wolfSSL to version 5.6.6 or later to eliminate the risk.
What to do
- Update debian wolfssl to version 5.6.6-1.2.
- Update wolfssl wolfssl to version 5.6.6 or later.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| Debian:12 | debian | wolfssl | All versions |
| Debian:13 | debian | wolfssl |
< 5.6.6-1.2 Fix: upgrade to 5.6.6-1.2
|
| – | wolfssl | wolfssl |
< 5.6.6 cpe:2.3:a:wolfssl:wolfssl:*:*:*:*:*:*:*:* |
Original advisory text
Improper (D)TLS key boundary enforcement
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.
References
- https://security-tracker.debian.org/tracker/CVE-2023-6937 Vendor Advisory
- https://github.com/wolfSSL/wolfssl Product
- https://www.wolfssl.com/docs/security-vulnerabilities/ Vendor Advisory
- https://github.com/wolfSSL/wolfssl/pull/7029 Patch
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/6xxx/CVE-2023-6937.j... Vendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2023-6937 Vendor Advisory
Internet-facing
14 days
Internal
60 days
- Not known to be exploited
- Can be exploited automatically
- Gives an attacker partial control
Severity
5.3
Medium
Type
CWE-20Improper Input Validation
Timeline
Published15 Feb 2024
Updated4 Nov 2026
First seen15 Sep 2026
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