CVE-2018-1000807: Python Cryptographic Authority pyopenssl version prior to version 17.5.0 contains a CWE-416: Use After Free vu

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HIGH 8.1REMOTEWATCHLISTUPGRADEMITIGATEDOWNGRADE

CVE-2018-1000807 is a high-severity flaw (CVSS 8.1) affecting pyopenssl, ubuntu linux, openstack. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Python Cryptographic Authority pyopenssl version prior to version 17.5.0 contains a CWE-416: Use After Free vulnerability in X509 object handling that can result in Use after free can lead to possible denial of service or remote code execution.. This attack appear to be exploitable via Depends on the calling application and if it retains a reference to the memory.. This vulnerability appears to have been fixed in 17.5.0.

Why this priority

High severity
EPSS top 9%: 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	8.1 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	4.1% (top 9%)
CISA exploited list	No
Weakness	CWE-416
Published	2018-10-08
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: canonical · pyopenssl · redhat

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2018-10-08 15:29 UTCPublished CVE record published
2026-06-17 01:33 UTCUpdated Record last modified

pyopenssl pyopenssl UPGRADE

Affected: < 17.5.0

Fixed in: 17.5.0

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 17.5.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade pyopenssl

Note

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

canonical ubuntu linux MITIGATE

Affected: 16.04

Fixed in: no fixed release known

Safe to downgrade to: a release before 16.04

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.

redhat openstack DOWNGRADE

Affected: 13

Fixed in: no fixed release known

Safe to downgrade to: a release before 13

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 13 (Debian / Ubuntu)

apt-cache madison openstack sudo apt install openstack=<VERSION_BEFORE_13> sudo apt-mark hold openstack

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list openstack sudo dnf downgrade openstack-<VERSION_BEFORE_13> sudo dnf versionlock add openstack

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

redhat enterprise linux desktop MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

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.

redhat enterprise linux server MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

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.

redhat enterprise linux workstation MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

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.

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-2018-1000807?

pyopenssl: upgrade to 17.5.0; ubuntu linux: mitigate or apply the listed mitigation; openstack: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2018-1000807 being exploited?

CVE-2018-1000807 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-2018-1000807 affect?

CVE-2018-1000807 affects pyopenssl, ubuntu linux, openstack. Severity is high (CVSS 8.1). Python Cryptographic Authority pyopenssl version prior to version 17.5.0 contains a CWE-416: Use After Free vulnerability in X509 object handling that can result in Use after free can lead to possible denial of service or remote code execut

How urgent is CVE-2018-1000807?

Priority 61/100. High severity; EPSS top 9%: very likely to be exploited; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Python vulnerabilities · Ubuntu vulnerabilities · OpenStack vulnerabilities

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References

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