CVE-2025-52881VulnerabilityPublished 6 Nov 2025

CVE-2025-52881: opencontainers runc · UNIX Symbolic Link (Symlink) Following

Affects opencontainers runcSource CVE Database V5

Mentioned vulnerabilities

CVE-2019-19921

Not known to be exploited · CVSS 7.3 High · fixed in 1.2.8 : patch opencontainers runc soon.

Data as of 26 Oct 2026, 08:30 UTC

CVSS 4.0 base score

7.3High

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

EPSS: 0.8% chance of exploitation in 30 days – higher than 56% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.2.8

CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

Attack Vector: Local
Attack Complexity: Low
Attack Requirements: Present
Privileges Required: Low
User Interaction: Active
Vulnerable system confidentiality: High
Vulnerable system integrity: High
Vulnerable system availability: High
Subsequent system confidentiality: High
Subsequent system integrity: High
Subsequent system availability: High

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

Attack Vector: Local: The vulnerable system 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 through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: Present: The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: a race condition must be won to successfully exploit the vulnerability (the successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker, or the attack may need to be launched multiple times against a single target before being successful); the attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: Active: Successful exploitation of this vulnerability requires a targeted user to perform specific, conscious interactions with the vulnerable system and the attacker’s payload, or the user’s interactions would actively subvert protection mechanisms which would lead to exploitation of the vulnerability.
Vulnerable system confidentiality: High: There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Vulnerable system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the vulnerable system.
Vulnerable system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Vulnerable System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).
Subsequent system confidentiality: High: There is a total loss of confidentiality, resulting in all resources within the Subsequent System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Subsequent system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the Subsequent System. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the Subsequent System.
Subsequent system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Subsequent System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Subsequent System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 6 Nov 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 Oct 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC 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
GitHubopencontainers/runc`pkg:github/opencontainers/runc`Other threats	Affected =1.2.7 =1.3.2	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

1. Upgrade runc to versions 1.2.8, 1.3.3, or 1.4.0-rc.3 or later immediately to apply the official fix. 2. Audit container configurations to identify and eliminate unnecessary shared mounts, especially tmpfs and bind mounts that could be manipulated via symlinks. 3. Implement strict mount namespace isolation and avoid sharing mounts between containers unless absolutely necessary. 4. Use container security tools to monitor and detect unusual symlink or mount activity during container runtime and build processes. 5. Harden CI/CD pipelines by restricting the use of docker buildx with custom shared mounts or applying additional validation on build configurations. 6. Employ Linux Security Modules (LSMs) such as SELinux or AppArmor with strict policies to limit container access to procfs and sensitive kernel interfaces. 7. Regularly review and update container runtime and orchestration tools to incorporate security patches and best practices. 8. Conduct penetration testing focused on container escape and privilege escalation vectors to validate mitigations.

Description

runc is a CLI tool for spawning and running containers according to the OCI specification. In versions 1.2.7, 1.3.2 and 1.4.0-rc.2, an attacker can trick runc into misdirecting writes to /proc to other procfs files through the use of a racing container with shared mounts (we have also verified this attack is possible to exploit using a standard Dockerfile with docker buildx build as that also permits triggering parallel execution of containers with custom shared mounts configured). This redirect could be through symbolic links in a tmpfs or theoretically other methods such as regular bind-mounts. While similar, the mitigation applied for the related CVE, CVE-2019-19921, was fairly limited and effectively only caused runc to verify that when LSM labels are written they are actually procfs files. This issue is fixed in versions 1.2.8, 1.3.3, and 1.4.0-rc.3.

Impact

For European organizations, the impact of CVE-2025-52881 is significant due to the widespread adoption of containerization technologies in cloud-native applications, DevOps pipelines, and microservices architectures. Exploitation could allow attackers to escalate privileges within container environments or escape container isolation, potentially compromising host systems and sensitive data. This could lead to unauthorized access to critical infrastructure, disruption of services, and data breaches. Organizations running vulnerable runc versions in production or CI/CD environments are at risk, especially if they use shared mounts or tmpfs in container configurations. The vulnerability undermines container security guarantees, increasing the attack surface for advanced persistent threats and insider attacks. Given the high CVSS score and the complexity of modern container deployments, the threat could affect cloud service providers, financial institutions, healthcare, and government sectors across Europe, where container adoption is robust.

Summary

CVE-2025-52881 is a vulnerability affecting opencontainers runc, a widely used CLI tool for spawning and running containers according to the OCI specification. The flaw exists in versions 1.2.7, 1.3.2, and 1.4.0-rc.2, where an attacker can exploit symbolic link following behavior in container environments that use shared mounts. Specifically, by orchestrating a race condition with containers that share mounts (such as tmpfs or bind mounts), an attacker can cause runc to misdirect writes intended for /proc files to other procfs files. This redirection is achieved through symlinks or other mount manipulation techniques, allowing unauthorized modification of procfs files, which can lead to privilege escalation or container escape. The vulnerability is similar in nature to CVE-2019-19921 but more severe due to broader scope and insufficient mitigation in previous patches. The issue can be exploited during container builds using docker buildx with custom shared mounts, increasing the attack surface. The vulnerability requires low privileges (PR:L), partial user interaction (UI:A), and has a high impact on confidentiality, integrity, and availability (all rated high). The vulnerability is fixed in runc versions 1.2.8, 1.3.3, and 1.4.0-rc.3. No known exploits are currently in the wild, but the complexity and potential impact warrant urgent attention.

CWE-61UNIX Symbolic Link (Symlink) Following (opens in a new tab)
Compound weaknessLikelihood of exploit: HighOWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.
Implementation
Symbolic link attacks often occur when a program creates a tmp directory that stores files/links. Access to the directory should be restricted to the program as to prevent attackers from manipulating the files.
Architecture and Design · Separation of Privilege
Follow the principle of least privilege when assigning access rights to entities in a software system.
OWASP Cheat Sheets
Authorization (opens in a new tab)
Attack patterns
Leveraging Race Conditions via Symbolic Links (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-363Race Condition Enabling Link Following (opens in a new tab)
Base weakness
The product checks the status of a file or directory before accessing it, which produces a race condition in which the file can be replaced with a link before the access is performed, causing the product to access the wrong file.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
OWASP ASVS 4.0.3
V1.11.2 (opens in a new tab)
V1.11.3 (opens in a new tab)
V11.1.6 (opens in a new tab)
Attack patterns
Leveraging Race Conditions (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 6 Nov 2025, 20:45 UTC

WeaknessesCWE-61, CWE-363

Technical details

References

Community reviews

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