{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata. Fed continuously.","feed_url":"https://feed.craftedsignal.io/tags/cve-2026-33747/feed.json","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cpes":[],"_cs_cves":[],"_cs_exploited":false,"_cs_has_poc":false,"_cs_poc_references":[],"_cs_products":["BuildKit"],"_cs_severities":["high"],"_cs_tags":["buildkit","file-escape","privilege-escalation","cve-2026-33747"],"_cs_type":"advisory","_cs_vendors":["Docker"],"content_html":"\u003cp\u003eCVE-2026-33747 describes a file escape vulnerability in BuildKit versions prior to v0.28.1. The vulnerability stems from a malicious BuildKit frontend's ability to craft API messages that cause files to be written outside of the designated BuildKit state directory for the execution context. This issue arises when using a custom, untrusted BuildKit frontend set via either the \u003ccode\u003e#syntax\u003c/code\u003e directive within a Dockerfile or through the \u003ccode\u003e--build-arg BUILDKIT_SYNTAX\u003c/code\u003e build argument. Exploitation requires the use of an untrusted frontend, and well-known frontends like \u003ccode\u003edocker/dockerfile\u003c/code\u003e are not affected. Successful exploitation allows an attacker to write arbitrary files to the host system, potentially leading to privilege escalation or code execution. Defenders should ensure BuildKit is updated to v0.28.1 or later and exercise caution when using custom frontends.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eAn attacker crafts a malicious BuildKit frontend.\u003c/li\u003e\n\u003cli\u003eThe victim builds an image using BuildKit, specifying the malicious frontend via \u003ccode\u003e#syntax\u003c/code\u003e in the Dockerfile or \u003ccode\u003e--build-arg BUILDKIT_SYNTAX\u003c/code\u003e.\u003c/li\u003e\n\u003cli\u003eBuildKit initiates the build process, handing control to the malicious frontend.\u003c/li\u003e\n\u003cli\u003eThe malicious frontend crafts a specific API message designed to exploit the file escape vulnerability.\u003c/li\u003e\n\u003cli\u003eBuildKit processes the crafted API message without proper validation of file paths.\u003c/li\u003e\n\u003cli\u003eThe malicious frontend instructs BuildKit to write a file to a location outside of the BuildKit state directory.\u003c/li\u003e\n\u003cli\u003eBuildKit, lacking sufficient path sanitization, writes the file to the attacker-controlled path on the host system.\u003c/li\u003e\n\u003cli\u003eThe attacker achieves arbitrary file write, potentially leading to code execution or privilege escalation.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful exploitation of CVE-2026-33747 allows an attacker to write arbitrary files on the host system where BuildKit is running. This can lead to a variety of consequences, including privilege escalation by overwriting system binaries, arbitrary code execution by placing malicious executables in startup directories, or data exfiltration by accessing sensitive files. The severity is high because it breaks container isolation and allows for host compromise. The number of potential victims is dependent on the adoption of BuildKit and the use of custom frontends.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eUpgrade BuildKit to version v0.28.1 or later to patch CVE-2026-33747.\u003c/li\u003e\n\u003cli\u003eExercise extreme caution when using custom BuildKit frontends. Avoid using untrusted frontends specified via \u003ccode\u003e#syntax\u003c/code\u003e or \u003ccode\u003e--build-arg BUILDKIT_SYNTAX\u003c/code\u003e.\u003c/li\u003e\n\u003cli\u003eImplement the provided Sigma rule \u003ccode\u003eDetect Suspicious BuildKit Frontend Usage\u003c/code\u003e to detect the usage of custom frontends.\u003c/li\u003e\n\u003cli\u003eImplement the provided Sigma rule \u003ccode\u003eDetect BuildKit File Creation Outside State Directory\u003c/code\u003e to detect file creation events.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2024-01-24T12:00:00Z","date_published":"2024-01-24T12:00:00Z","id":"https://feed.craftedsignal.io/briefs/2024-01-buildkit-file-escape/","summary":"A malicious BuildKit frontend can craft API messages that write files outside the BuildKit state directory, leading to file escape, fixed in v0.28.1+ and requires using an untrusted frontend with `#syntax` or `--build-arg BUILDKIT_SYNTAX`.","title":"BuildKit Malicious Frontend File Escape Vulnerability","url":"https://feed.craftedsignal.io/briefs/2024-01-buildkit-file-escape/"}],"language":"en","title":"CraftedSignal Threat Feed - Cve-2026-33747","version":"https://jsonfeed.org/version/1.1"}