CVE-2026-33711
Linuxcontainers Incus ≤ 6.23.0
Raw vector
CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XSummary
CVE-2026-33711 is a medium-severity UNIX Symbolic Link (Symlink) Following (CWE-61) vulnerability in Linuxcontainers Incus. Its CVSS base score is 4.7 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Path Interception (T1034); ranked at the 28th 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 AC-3 (Access Enforcement) and AC-4 (Information Flow Enforcement) — 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-2026-33711 is a symlink attack vulnerability (CWE-61) in Incus, an open-source system container and virtual machine manager. The issue affects the API endpoint for retrieving VM screenshots, which uses predictable temporary file paths under /tmp for QEMU to write screenshot data before it is served to the user and deleted. Versions of Incus prior to 6.23.0 are vulnerable, with a CVSS v3.1 base score of 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).
A local attacker with low privileges can exploit this by pre-creating symlinks at the predictable /tmp paths. On most Linux systems, the kernel's protected_symlinks feature prevents success, resulting in a "Permission denied" error. However, on rare systems where protected_symlinks is explicitly disabled, the attacker can trick Incus into truncating arbitrary files and modifying their mode and permissions, potentially causing denial of service or local privilege escalation.
The Incus security advisory (GHSA-q9vp-3wcg-8p4x) confirms that upgrading to version 6.23.0 resolves the issue by addressing the predictable temporary file usage. Security practitioners should verify protected_symlinks is enabled on Linux hosts running Incus and prioritize patching affected instances.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-16462
Vulnerability Data
Incus is a system container and virtual machine manager. Incus provides an API to retrieve VM screenshots. That API relies on the use of a temporary file for QEMU to write the screenshot to which is then picked up and…
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sent to the user prior to deletion. As versions prior to 6.23.0 use predictable paths under /tmp for this, an attacker with local access to the system can abuse this mechanism by creating their own symlinks ahead of time. On the vast majority of Linux systems, this will result in a "Permission denied" error when requesting a screenshot. That's because the Linux kernel has a security feature designed to block such attacks, `protected_symlinks`. On the rare systems with this purposefully disabled, it's then possible to trick Incus intro truncating and altering the mode and permissions of arbitrary files on the filesystem, leading to a potential denial of service or possible local privilege escalation. Version 6.23.0 fixes the issue.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 2 hardening rules · 2 OS baselines
V5.2.5
Mitigating Controls (NIST 800-53 r5) AI
Access enforcement must resolve the actual target of any file reference and apply authorizations to it, directly stopping symlink traversal to unauthorized objects.
Information-flow enforcement on file operations must follow the resolved target rather than the link name, blocking unauthorized data movement via symlinks.
Least-privilege restrictions on the directories that may contain links or targets reduce the set of files an attacker can reach even if a symlink is followed.
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 prevent introduction of symlink-following flaws in file-handling code.
Vulnerability identification can discover existing symlink issues but does not prevent or remediate them in code.
Least-privilege access policies can limit damage from symlink attacks but do not address the coding flaw itself.
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.
Security testing can detect symlink-following vulnerabilities before deployment, covering most of the weakness.
Secure-architecture principles require safe file-handling and canonicalization, directly addressing symlink attacks.
Secure-coding standards mandate explicit symlink checks and safe open patterns, fully mitigating CWE-61.
Access-control rules can restrict which files a process may open, reducing symlink-following risk but not eliminating the underlying path-resolution flaw.
Configuration management can enforce safe file-permission baselines that limit symlink abuse, but does not address the code flaw itself.
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).
Oracle Linux 8 (1 rule)
- V-248577 OL 8 must enable kernel parameters to enforce Discretionary Access Control (DAC) on symlinks. prevents CWE-61