CVE-2026-1386: CWE-61: UNIX Symbolic Link (Symlink) Following in AWS Firecracker
Bulletin ID: 2026-003-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 2026/01/23 12:30 PM PST Description: Firecracker is an open source virtualization technology that is purpose-built for creating and managing secure, multi-tenant container and function-based services. Firecracker runs in user space and uses the Linux Kernel-based Virtual Machine (KVM) to create microVMs. Each Firecracker microVM is further isolated with common Linux user-space security barriers by a companion program called "jailer". The jailer provides a second line of defense in case a user escapes from the microVM boundaries and it is released at each Firecracker version. We are aware of CVE-2026-1386, an issue that is related to the Firecracker jailer, which under certain circumstances can allow an user to overwrite arbitrary files in the host filesystem. AWS services that use Firecracker are not impacted by the issue as we appropriately restrict access to the host and the jailer folder, blocking the preconditions required for the attack to happen. Impacted versions: Firecracker version v1.13.1 and earlier and 1.14.0 Please refer to the article below for the most up-to-date and complete information related to this AWS Security Bulletin.
AI Analysis
Technical Summary
This vulnerability (CVE-2026-1386) affects the jailer component of AWS Firecracker on Linux systems. It is caused by improper handling of UNIX symbolic links, allowing a local user with write permissions to the jailer directories to create symlinks that the jailer follows during startup. If the jailer process runs with root privileges, this can lead to arbitrary host file overwrites. The issue is present in Firecracker versions v1.13.1 and earlier, and 1.14.0. AWS recommends upgrading to Firecracker version v1.13.2 or 1.14 to fix the vulnerability.
Potential Impact
An attacker with local write access to the jailer directories can exploit this vulnerability to overwrite arbitrary files on the host system during jailer startup if the jailer runs with root privileges. This can lead to integrity and availability impacts on the host system. The CVSS score of 6.0 reflects a medium severity with high impact on integrity and availability, but no confidentiality impact.
Mitigation Recommendations
AWS recommends upgrading to Firecracker version v1.13.2 or 1.14, where this vulnerability is fixed. Since this is not a cloud service but a software component, users should apply the official patch by upgrading to the fixed versions. Patch status is confirmed by the vendor advisory recommending these versions.
CVE-2026-1386: CWE-61: UNIX Symbolic Link (Symlink) Following in AWS Firecracker
Description
Bulletin ID: 2026-003-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 2026/01/23 12:30 PM PST Description: Firecracker is an open source virtualization technology that is purpose-built for creating and managing secure, multi-tenant container and function-based services. Firecracker runs in user space and uses the Linux Kernel-based Virtual Machine (KVM) to create microVMs. Each Firecracker microVM is further isolated with common Linux user-space security barriers by a companion program called "jailer". The jailer provides a second line of defense in case a user escapes from the microVM boundaries and it is released at each Firecracker version. We are aware of CVE-2026-1386, an issue that is related to the Firecracker jailer, which under certain circumstances can allow an user to overwrite arbitrary files in the host filesystem. AWS services that use Firecracker are not impacted by the issue as we appropriately restrict access to the host and the jailer folder, blocking the preconditions required for the attack to happen. Impacted versions: Firecracker version v1.13.1 and earlier and 1.14.0 Please refer to the article below for the most up-to-date and complete information related to this AWS Security Bulletin.
CVSS v3.1
Score 6.0medium
Affected software
pkg:github/firecracker-microvm/firecrackerRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability (CVE-2026-1386) affects the jailer component of AWS Firecracker on Linux systems. It is caused by improper handling of UNIX symbolic links, allowing a local user with write permissions to the jailer directories to create symlinks that the jailer follows during startup. If the jailer process runs with root privileges, this can lead to arbitrary host file overwrites. The issue is present in Firecracker versions v1.13.1 and earlier, and 1.14.0. AWS recommends upgrading to Firecracker version v1.13.2 or 1.14 to fix the vulnerability.
Potential Impact
An attacker with local write access to the jailer directories can exploit this vulnerability to overwrite arbitrary files on the host system during jailer startup if the jailer runs with root privileges. This can lead to integrity and availability impacts on the host system. The CVSS score of 6.0 reflects a medium severity with high impact on integrity and availability, but no confidentiality impact.
Mitigation Recommendations
AWS recommends upgrading to Firecracker version v1.13.2 or 1.14, where this vulnerability is fixed. Since this is not a cloud service but a software component, users should apply the official patch by upgrading to the fixed versions. Patch status is confirmed by the vendor advisory recommending these versions.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- AMZN
- Date Reserved
- 2026-01-23T20:11:49.349Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6973dbae4623b1157c62ac34
Added to database: 01/23/2026, 20:35:58 UTC
Last enriched: 06/05/2026, 19:27:48 UTC
Last updated: 08/19/2026, 22:52:10 UTC
Views: 464
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