CVE-2018-0737: The OpenSSL RSA Key generation algorithm has been shown to be vulnerable to a cache timing side channel attack

Q: How do I fix CVE-2018-0737?

openssl: upgrade to newer than 1.1.0h; ubuntu linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2018-0737 being exploited?

CVE-2018-0737 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-2018-0737 affect?

CVE-2018-0737 affects openssl, ubuntu linux. Severity is medium (CVSS 5.9). The OpenSSL RSA Key generation algorithm has been shown to be vulnerable to a cache timing side channel attack. An attacker with sufficient access to mount cache timing attacks during the RSA key generation process could recover the private

Q: How urgent is CVE-2018-0737?

Priority 55/100. EPSS top 4%: very likely to be exploited; Remotely exploitable, no login, no user action; On your watchlist

This week

MEDIUM 5.9REMOTEWATCHLISTUPGRADEMITIGATE

CVE-2018-0737 is a medium-severity flaw (CVSS 5.9) affecting openssl, ubuntu linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The OpenSSL RSA Key generation algorithm has been shown to be vulnerable to a cache timing side channel attack. An attacker with sufficient access to mount cache timing attacks during the RSA key generation process could recover the private key. Fixed in OpenSSL 1.1.0i-dev (Affected 1.1.0-1.1.0h). Fixed in OpenSSL 1.0.2p-dev (Affected 1.0.2b-1.0.2o).

Why this priority

EPSS top 4%: very likely to be exploited
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	11.6% (top 4%)
CISA exploited list	No
Weakness	CWE-327
Published	2018-04-16
Last modified	2026-10-15

Publisher (CNA): OpenSSL Software Foundation · Vendor: canonical · openssl

Last updated 2026-10-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2018-04-16 18:29 UTCPublished CVE record published
2026-10-15 18:17 UTCUpdated Record last modified

openssl openssl UPGRADE

Affected: >= 1.0.2b and <= 1.0.2o · >= 1.1.0 and <= 1.1.0h

Fixed in: newer than 1.1.0h

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 1.1.0h (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade openssl

Note

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

canonical ubuntu linux MITIGATE

Affected: 14.04 · 16.04 · 17.10

Fixed in: no fixed release known

Safe to downgrade to: a release before 14.04

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-2018-0737?

openssl: upgrade to newer than 1.1.0h; ubuntu linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2018-0737 being exploited?

CVE-2018-0737 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-2018-0737 affect?

CVE-2018-0737 affects openssl, ubuntu linux. Severity is medium (CVSS 5.9). The OpenSSL RSA Key generation algorithm has been shown to be vulnerable to a cache timing side channel attack. An attacker with sufficient access to mount cache timing attacks during the RSA key generation process could recover the private

How urgent is CVE-2018-0737?

Priority 55/100. EPSS top 4%: very likely to be exploited; Remotely exploitable, no login, no user action; On your watchlist

Software pages

OpenSSL vulnerabilities · Ubuntu vulnerabilities

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References

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