CVE-2020-24659: An issue was discovered in GnuTLS before 3.6.15

Q: How do I fix CVE-2020-24659?

gnutls: upgrade to 3.6.15; fedora: mitigate or apply the listed mitigation; leap: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2020-24659 being exploited?

CVE-2020-24659 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2020-24659 affect?

CVE-2020-24659 affects gnutls, fedora, leap. Severity is high (CVSS 7.5). 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

Q: How urgent is CVE-2020-24659?

Priority 64/100. High severity; EPSS top 10%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

This week

HIGH 7.5REMOTEWATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2020-24659 is a high-severity flaw (CVSS 7.5) affecting gnutls, fedora, leap. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity
EPSS top 10%: very likely to be exploited
Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	3.8% (top 10%)
CISA exploited list	No
Weakness	CWE-476, CWE-787
Published	2020-09-04
Last modified	2026-10-14

Publisher (CNA): MITRE · Vendor: canonical · fedoraproject · gnu · opensuse

Last updated 2026-10-14 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-09-04 15:15 UTCPublished CVE record published
2026-10-14 10:17 UTCUpdated Record last modified

gnu gnutls UPGRADE

Affected: < 3.6.15

Fixed in: 3.6.15

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy gnutls || rpm -q gnutls || gnutls --version

2. UPGRADE to 3.6.15 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade gnutls

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade gnutls

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

fedoraproject fedora MITIGATE

Affected: 32 · 33

Fixed in: no fixed release known

Safe to downgrade to: a release before 32

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

opensuse leap MITIGATE

Affected: 15.1 · 15.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 15.1

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

canonical ubuntu linux MITIGATE

Affected: 20.04

Fixed in: no fixed release known

Safe to downgrade to: a release before 20.04

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-24659?

gnutls: upgrade to 3.6.15; fedora: mitigate or apply the listed mitigation; leap: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-24659 being exploited?

CVE-2020-24659 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-24659 affect?

CVE-2020-24659 affects gnutls, fedora, leap. Severity is high (CVSS 7.5). 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

How urgent is CVE-2020-24659?

Priority 64/100. High severity; EPSS top 10%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Ubuntu vulnerabilities · GnuTLS vulnerabilities

Related CVEs

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CVE-2026-33845 HIGH 7.5 MITIGATE DOWNGRADE A flaw in GnuTLS DTLS handshake parsing allows malformed fragments with zero length and non-zero offset, leadi
CVE-2026-1584 HIGH 7.5 MITIGATE MITIGATE A flaw was found in gnutls
CVE-2026-3833 MEDIUM 6.5 MITIGATE MITIGATE A flaw was found in gnutls

References

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