Description

A malicious builder peer may be able to request an in-context file by name from the host and receive the contents of whatever the name resolves to, even when it resolves outside the build context. This vulnerability is addressed in container version 1.2.0.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "4.3",
  "pubDate": "2026-08-20T19:16:57.733Z",
  "pubdate": "2026-08-20T19:16:57.733Z",
  "executiveSummary": "This vulnerability involves an arbitrary file read flaw within the container build mechanism, specifically affecting container version 1.2.0 and prior. The security defect allows a malicious builder peer to request arbitrary files from the host system by specifying target file names directly, bypassing standard boundary enforcement mechanisms. Consequently, the resolution mechanism permits traversal outside the designated build context, exposing sensitive host-level files to unauthorized entities.\nThe primary impact of this vulnerability is the unauthorized disclosure of sensitive data residing on the host system, which may include configuration files, credentials, source code, or system-level data accessible to the container build process. The risk implications are severe, as internal host reconnaissance or credential harvesting can facilitate further compromise of the infrastructure.\nAttacker capabilities are limited to entities participating as builder peers within the build ecosystem, who can manipulate file path requests during the in-context file retrieval phase. Exploitation requires the ability to communicate as a builder peer and issue crafted file name requests designed to traverse or point outside the constrained build boundaries. Mitigation requires updating the affected software to container version 1.2.0 or later, where path validation and boundary checks have been properly enforced to restrict file resolution strictly to the authorized build context.",
  "technicalDetails": "The vulnerability exists within the file resolution and handling component of the container building system, which processes requests for in-context files from builder peers. The root cause stems from insufficient input sanitization and a lack of rigorous path validation when resolving requested file names against the host filesystem. Specifically, the path resolution logic fails to verify whether the canonicalized path of the requested file remains within the boundaries of the authorized build context directory.\nDuring the exploitation phase, a malicious builder peer initiates a request for an in-context file by supplying a specific file name or path traversal sequence. Because the vulnerable component improperly handles the name resolution, the operating system evaluates the path against the host filesystem without adequate confinement. As a result, the backend service retrieves the contents of whatever resource the supplied name resolves to, even if the target resides completely outside the intended build context.\nThe attack flow proceeds as follows: First, the malicious peer establishes communication with the builder service. Second, the attacker crafts a specialized request referencing a sensitive file path on the host. Third, the vulnerable component processes the request and resolves the path on the host filesystem. Fourth, the host system reads the target file contents and transmits them back to the requesting builder peer. The payload behavior involves the extraction of arbitrary host files, leading to immediate post-exploitation information disclosure. Network exposure and authentication requirements depend on the specific peer-to-peer communication model utilized by the container builder network, while privilege requirements correspond to the execution context of the builder service on the host."
}