VulnerabilityPublished 27 Jun 2025

CVE-2025-52991: NixOS Nix · Incorrect Default Permissions

Affects NixOS NixSource CVE Database V5

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Not known to be exploited · CVSS 3.2 Low.

Data as of 2 Nov 2026, 10:57 UTC

CVSS 3.1 base score

3.2Low

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N

Attack Vector: Local
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: None
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 27 Jun 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
NixOS Nix	Affected 0 – 2.29.0 4 affected builds	Fixed in–

AI-suggested

To mitigate CVE-2025-52991, European organizations should implement the following specific measures: 1) Upgrade all affected package managers (Nix, Lix, Guix) to the latest patched versions where the default permissions for temporary build directories are corrected to restrict access appropriately. 2) Enforce strict file system permissions on temporary build directories, ensuring they are accessible only to the user performing the build process. 3) Isolate build environments using containerization or sandboxing techniques to prevent unauthorized users from accessing or manipulating build directories. 4) Implement robust access controls and user segregation on build servers and developer workstations to minimize the risk of untrusted users interfering with build processes. 5) Monitor build logs and artifacts for anomalies that could indicate tampering or unauthorized modifications. 6) Incorporate integrity verification mechanisms such as reproducible builds and cryptographic signing of build outputs to detect unauthorized changes. 7) Educate developers and system administrators about the risks of improper permissions and the importance of secure build environments. These targeted actions go beyond generic advice by focusing on build environment hardening and process integrity specific to the affected package managers.

Description

The Nix, Lix, and Guix package managers default to using temporary build directories in a world-readable and world-writable location. This allows standard users to deceive the package manager into using directories with pre-existing content, potentially leading to unauthorized actions or data manipulation. This affects Nix before 2.24.15, 2.26.4, 2.28.4, and 2.29.1; Lix before 2.91.2, 2.92.2, and 2.93.1; and Guix before 1.4.0-38.0e79d5b.

Impact

For European organizations, the impact of CVE-2025-52991 is primarily on the integrity of software packages built using the affected package managers. Organizations relying on Nix, Lix, or Guix for software deployment or development could face risks of unauthorized code injection or tampering during package builds if untrusted users have local access to build environments. This could lead to compromised software integrity, potentially introducing backdoors or malicious payloads into production environments. However, the low CVSS score and the requirement for local access with no privileges reduce the likelihood of widespread exploitation. Organizations with multi-user development environments, shared build servers, or CI/CD pipelines using these package managers are at higher risk. The vulnerability does not affect confidentiality or availability directly but undermines trust in the software supply chain, which is critical for compliance and security assurance in European industries, especially those under strict regulatory frameworks like GDPR and NIS Directive.

CWE-276Incorrect Default Permissions (opens in a new tab)
Base weaknessLikelihood of exploit: MediumOWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
During installation, installed file permissions are set to allow anyone to modify those files.
Architecture and Design · Operation
The architecture needs to access and modification attributes for files to only those users who actually require those actions.
Architecture and Design · Separation of Privilege
Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
OWASP Cheat Sheets
Access Control (opens in a new tab)
Authorization Testing Automation (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.8 (opens in a new tab)
V13.4.2 (opens in a new tab)
Attack patterns
Accessing Functionality Not Properly Constrained by ACLs (opens in a new tab)
Directory Indexing (opens in a new tab)
Web Server Logs Tampering (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 27 Jun 2025, 14:54 UTC

WeaknessesCWE-276

Technical details

References

Community reviews

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