CVE-2026-5747: Out-of-bounds Write in Firecracker virtio-pci Transport

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of 29 Oct 2026. If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?

0.3%

Up from 0.2% on 22 Oct 2026.

EPSS score, percentile 17.3 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

8.7 High

CVSS v4.0 base score, given by the CNA

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

Advisories and patches (3)

Which versions are affected?

Affected

• 1.13.0 through 1.14.3
• 1.15.0

Unaffected 1.14.4; 1.15.1

Versions by product

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 29 Oct 2026. About the data.

What to do

Advisories and patches

• github.com (Patch)
• github.com (Patch)
• aws.amazon.com (Vendor advisory)

This summary is based on the CVE record as of 29 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

As listed in the CVE record.

Versions not listed are: unaffected.

Versions the record lists as unaffected: 1.14.4, 1.15.1.

Source: CVE List, as of 29 Oct 2026. About the data.

About this vulnerability

An out-of-bounds write issue in the virtio PCI transport in Firecracker 1.13.0 through 1.14.3 and 1.15.0 on x86_64 and aarch64 might allow a local guest user with root privileges to crash the Firecracker VMM process or potentially execute arbitrary code on the host via modification of virtio queue configuration registers after device activation. Achieving code execution on the host requires addit…

Summary: CVE record, as of 29 Oct 2026.

• CISA has not added CVE-2026-5747 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
• The CVE record was published on 7 Apr 2026.
• The CVE record carries a CVSS v4.0 base score of 8.7 (High), given by its CNA.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.3% (percentile 17.3), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
• CISA's SSVC assessment in the CVE record: exploitation none, automatable no, technical impact total.
• The credits in the CVE record name Anthropic (Claude) as finder.

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; CVE List, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026. About the data.

Description

Out-of-bounds Write in Firecracker virtio-pci Transport

An out-of-bounds write issue in the virtio PCI transport in Firecracker 1.13.0 through 1.14.3 and 1.15.0 on x86_64 and aarch64 might allow a local guest user with root privileges to crash the Firecracker VMM process or potentially execute arbitrary code on the host via modification of virtio queue configuration registers after device activation. Achieving code execution on the host requires additional preconditions, such as the use of a custom guest kernel or specific snapshot configurations. To remediate this, users should upgrade to Firecracker 1.14.4 or 1.15.1 and later.

Source: CVE List, as of 29 Oct 2026. About the data.

Timeline