CVE-2026-34178
Canonical Lxd 4.12 – 5.0.6
Raw vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:HSummary
CVE-2026-34178 is a critical-severity Improper Input Validation (CWE-20) vulnerability in Canonical Lxd. Its CVSS base score is 9.1 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 35th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-34178 is an improper input validation vulnerability (CWE-20) in Canonical LXD versions prior to 6.8. The issue lies in the backup import functionality, where project restrictions are enforced by validating the backup/index.yaml file within a supplied tar archive. However, the instance is actually created using the separate backup/container/backup.yaml file, which is not checked against project restrictions. This discrepancy allows attackers to embed unauthorized configurations in the unchecked file. The vulnerability carries a CVSS v3.1 base score of 9.1 (AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H), indicating critical severity due to its potential for high-impact exploitation.
An authenticated remote attacker with instance-creation permissions in a restricted LXD project can exploit this by crafting a malicious tar archive backup. By placing restricted settings, such as security.privileged=true or raw.lxc directives, into the backup.yaml file while ensuring index.yaml passes validation, the attacker bypasses all project restrictions during import. Successful exploitation enables creation of a privileged container, leading to full host compromise through container escape and arbitrary code execution on the underlying system.
Mitigation is addressed in the referenced GitHub security advisory (GHSA-q96j-3fmm-7fv4) and pull request #17921, which patch the validation logic in LXD 6.8 and later versions. Security practitioners should upgrade to LXD 6.8 or higher and review access controls for instance-creation permissions in restricted projects to prevent exploitation.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-20874
Vulnerability Data
In Canonical LXD before 6.8, the backup import path validates project restrictions against backup/index.yaml in the supplied tar archive but creates the instance from backup/container/backup.yaml, a separate file in the same archive that is never checked against project restrictions. An…
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authenticated remote attacker with instance-creation permission in a restricted project can craft a backup archive where backup.yaml carries restricted settings such as security.privileged=true or raw.lxc directives, bypassing all project restriction enforcement and allowing full host compromise.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 6 hardening rules · 3 OS baselines
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Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation can discover missing input validation through analysis or test cases.
SI-10 directly requires validity checks on information inputs, structurally preventing improper or missing validation.
Requiring documented development standards and tools can embed input-validation practices into the engineering process.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly require and enforce input validation during development.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Testing against a defined set of requirements and using code review plus vulnerability scanning forces validation of inputs and handling of unanticipated conditions, reducing the chance that malformed data will be accepted.
Secure-coding guidelines and mandatory security testing (including code scans) compel developers to validate and sanitize inputs at design and implementation time, lowering the incidence of malformed or malicious data reaching downstream components.
Mandating input controls that include integrity checks and input validation ensures that untrusted data is examined before use, blocking the root cause of many injection and malformed-data weaknesses.
Security-by-design principles explicitly call for data validation and sanitization at every layer, reducing the chance that malformed or malicious input will be processed without scrutiny.
Requiring language-specific secure coding standards, peer review, SAST and documented mitigation of common programming errors forces validation of all inputs before they are trusted.
Regular automated validation of system software and data content, combined with scanning of all inbound files, enforces input validation at the boundary before untrusted content is processed.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
RHEL 8 (1 rule)
- V-230265 RHEL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-20