CVE-2023-5981: A vulnerability was found that the response times to malformed ciphertexts in RSA-PSK ClientKeyExchange differ

Q: How do I fix CVE-2023-5981?

debian linux: mitigate or apply the listed mitigation; gnutls: upgrade to 3.8.2; linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2023-5981 being exploited?

CVE-2023-5981 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-2023-5981 affect?

CVE-2023-5981 affects debian linux, gnutls, linux. Severity is medium (CVSS 5.9). A vulnerability was found that the response times to malformed ciphertexts in RSA-PSK ClientKeyExchange differ from response times of ciphertexts with correct PKCS#1 v1.5 padding.

Q: How urgent is CVE-2023-5981?

Priority 48/100. Remotely exploitable, no login, no user action; On your watchlist

This month

MEDIUM 5.9REMOTEWATCHLISTMITIGATEUPGRADEMITIGATE

CVE-2023-5981 is a medium-severity flaw (CVSS 5.9) affecting debian linux, gnutls, linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A vulnerability was found that the response times to malformed ciphertexts in RSA-PSK ClientKeyExchange differ from response times of ciphertexts with correct PKCS#1 v1.5 padding.

Why this priority

Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	1.3% (top 30%)
CISA exploited list	No
Weakness	CWE-208, CWE-203
Published	2023-11-28
Last modified	2026-10-14

Publisher (CNA): Red Hat, Inc. · Vendor: debian · fedoraproject · gnu · redhat

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

Am I affected?

Timeline

2023-11-28 12:15 UTCPublished CVE record published
2026-10-14 22:17 UTCUpdated Record last modified

debian debian linux MITIGATE

Affected: 10.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.0

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.

gnu gnutls UPGRADE

Affected: < 3.8.2

Fixed in: 3.8.2

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 3.8.2 (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.

redhat linux MITIGATE

Affected: 8.0 · 9.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0

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.

fedoraproject fedora MITIGATE

Affected: 37 · 38

Fixed in: no fixed release known

Safe to downgrade to: a release before 37

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-2023-5981?

debian linux: mitigate or apply the listed mitigation; gnutls: upgrade to 3.8.2; linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2023-5981 being exploited?

CVE-2023-5981 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-2023-5981 affect?

CVE-2023-5981 affects debian linux, gnutls, linux. Severity is medium (CVSS 5.9). A vulnerability was found that the response times to malformed ciphertexts in RSA-PSK ClientKeyExchange differ from response times of ciphertexts with correct PKCS#1 v1.5 padding.

How urgent is CVE-2023-5981?

Priority 48/100. Remotely exploitable, no login, no user action; On your watchlist

Software pages

Debian vulnerabilities · GnuTLS vulnerabilities

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References

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