CVE-2017-1000256: libvirt version 2.3.0 and later is vulnerable to a bad default configuration of "verify-peer=no" passed to QEM

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HIGH 8.1REMOTEWATCHLISTUPGRADEMITIGATE

CVE-2017-1000256 is a high-severity flaw (CVSS 8.1) affecting libvirt, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

libvirt version 2.3.0 and later is vulnerable to a bad default configuration of "verify-peer=no" passed to QEMU by libvirt resulting in a failure to validate SSL/TLS certificates by default.

Why this priority

High severity
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	1.7% (top 23%)
CISA exploited list	No
Weakness	CWE-295
Published	2017-10-31
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: debian · redhat

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

Am I affected?

Timeline

2017-10-31 15:29 UTCPublished CVE record published
2026-06-17 00:59 UTCUpdated Record last modified

redhat libvirt UPGRADE

Affected: >= 2.3.0 and < 3.9.0

Fixed in: 3.9.0

Safe to downgrade to: a release before 2.3.0

1. Check installed version

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

2. UPGRADE to 3.9.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libvirt

Note

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

3. If no update is available yet, DOWNGRADE to a release before 2.3.0 (Debian / Ubuntu)

apt-cache madison libvirt sudo apt install libvirt=<VERSION_BEFORE_2.3.0> sudo apt-mark hold libvirt

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list libvirt sudo dnf downgrade libvirt-<VERSION_BEFORE_2.3.0> sudo dnf versionlock add libvirt

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.

debian debian linux MITIGATE

Affected: 9.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.0

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-2017-1000256?

libvirt: upgrade to 3.9.0; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2017-1000256 being exploited?

CVE-2017-1000256 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-2017-1000256 affect?

CVE-2017-1000256 affects libvirt, debian linux. Severity is high (CVSS 8.1). libvirt version 2.3.0 and later is vulnerable to a bad default configuration of "verify-peer=no" passed to QEMU by libvirt resulting in a failure to validate SSL/TLS certificates by default.

How urgent is CVE-2017-1000256?

Priority 58/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Debian vulnerabilities · QEMU vulnerabilities

Related CVEs

CVE-2024-8235 MEDIUM 6.2 UPGRADE A flaw was found in libvirt
CVE-2024-2496 MEDIUM 5.0 UPGRADE MITIGATE A NULL pointer dereference flaw was found in the udevConnectListAllInterfaces() function in libvirt
CVE-2023-3750 MEDIUM 6.5 MITIGATE MITIGATE A flaw was found in libvirt
CVE-2023-2700 MEDIUM 5.5 DOWNGRADE MITIGATE A vulnerability was found in libvirt
CVE-2022-0897 MEDIUM 4.3 UPGRADE MITIGATE A flaw was found in the libvirt nwfilter driver

References

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