HIGH

CVE-2020-24659

Q: What is CVE-2020-24659?

An issue was discovered in GnuTLS before 3.6.15. A server can trigger a NULL pointer dereference in a TLS 1.3 client if a no_renegotiation alert is sent with unexpected timing, and then an invalid second handshake occurs. The crash happens in the application's error handling path, where the gnutls_deinit function is called after detecting a handshake failure.

Q: Is CVE-2020-24659 actively exploited?

Active exploitation of CVE-2020-24659 has not been confirmed. Its EPSS score was 3.8% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2020-24659?

CVE-2020-24659 has a CVSS v3 base score of 7.5 (HIGH severity).

CVSS v3

7.5

HIGH

EPSS Score

3.8 %

exploit probability, as of 2026-10-19

CISA KEV

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

CVE-2020-24659 Red Hat Product Security75 products fixed
gnutls: Heap buffer overflow in handshake with no_renegotiation alert sent
ICSA-23-348-10 CISA5 known affected
Siemens SIMATIC S7-1500
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) · SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)
SSA-398330 Siemens ProductCERT5 known affected
SSA-398330: Vulnerabilities in the additional GNU/Linux subsystem of the SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP >= V3.1.0 and < V3.1.5
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= V3.1.0 < V3.1.5 · SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= V3.1.0 < V3.1.5 · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= V3.1.0 < V3.1.5
RHSA-2020:5483 Red Hat Product Security75 products fixed
Red Hat Security Advisory: gnutls security and bug fix update

Full record on NVD

Description

An issue was discovered in GnuTLS before 3.6.15. A server can trigger a NULL pointer dereference in a TLS 1.3 client if a no_renegotiation alert is sent with unexpected timing, and then an invalid second handshake occurs. The crash happens in the application's error handling path, where the gnutls_deinit function is called after detecting a handshake failure.

Technical details

Published: 2020-09-04

Frequently asked questions

What is CVE-2020-24659?

Is CVE-2020-24659 actively exploited?

Active exploitation of CVE-2020-24659 has not been confirmed. Its EPSS score was 3.8% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2020-24659?

CVE-2020-24659 has a CVSS v3 base score of 7.5 (HIGH severity).

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