{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata. Fed continuously.","feed_url":"https://feed.craftedsignal.io/tags/dav/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":["NGINX Open Source","NGINX Plus"],"_cs_severities":["high"],"_cs_tags":["nginx","dav","buffer-overflow","cve-2026-27654","denial-of-service"],"_cs_type":"advisory","_cs_vendors":["NGINX"],"content_html":"\u003cp\u003eCVE-2026-27654 describes a buffer overflow vulnerability found within the \u003ccode\u003engx_http_dav_module\u003c/code\u003e module in NGINX Open Source and NGINX Plus. This vulnerability can be triggered when the NGINX configuration utilizes the DAV module's MOVE or COPY methods in conjunction with prefix location definitions (non-regular expression location configuration) and alias directives. Successful exploitation of this flaw could allow an attacker to cause the NGINX worker process to terminate, leading to a denial-of-service condition. Additionally, it may be possible to modify source or destination file names outside the intended document root, though the impact is limited by the low privileges typically assigned to the NGINX worker process user. This vulnerability affects systems using vulnerable versions of NGINX Open Source and NGINX Plus with the specified configuration patterns.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eAn attacker identifies a vulnerable NGINX server utilizing the \u003ccode\u003engx_http_dav_module\u003c/code\u003e with MOVE or COPY methods enabled, along with prefix location configurations and alias directives.\u003c/li\u003e\n\u003cli\u003eThe attacker crafts a malicious HTTP request targeting a specific DAV endpoint configured with a prefix location and alias. This request uses either the MOVE or COPY method.\u003c/li\u003e\n\u003cli\u003eThe crafted request includes oversized or specially formatted parameters within the HTTP headers or body, designed to trigger a buffer overflow in the \u003ccode\u003engx_http_dav_module\u003c/code\u003e's processing logic.\u003c/li\u003e\n\u003cli\u003eThe NGINX worker process receives the malicious request and attempts to process it using the vulnerable code path in the \u003ccode\u003engx_http_dav_module\u003c/code\u003e.\u003c/li\u003e\n\u003cli\u003eThe buffer overflow occurs during the processing of the MOVE or COPY operation, potentially overwriting adjacent memory regions within the NGINX worker process.\u003c/li\u003e\n\u003cli\u003eDepending on the nature of the overflow, this can lead to one of two outcomes: either the NGINX worker process crashes, resulting in a denial-of-service, or...\u003c/li\u003e\n\u003cli\u003e...the attacker gains limited control over file operations, potentially modifying file names outside the designated document root by manipulating memory related to file paths.\u003c/li\u003e\n\u003cli\u003eThe attacker achieves either denial of service through worker process termination or limited unauthorized file modifications within the constraints of the worker process user's privileges.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful exploitation of CVE-2026-27654 can result in a denial-of-service condition affecting the targeted NGINX web server. While the integrity impact is constrained due to the low privileges of the NGINX worker process user, attackers may be able to modify file names outside of the intended document root. The number of affected systems depends on the prevalence of NGINX configurations that utilize the vulnerable \u003ccode\u003engx_http_dav_module\u003c/code\u003e in conjunction with the specific MOVE/COPY, prefix location, and alias directive patterns. The vulnerability primarily impacts web applications and services reliant on the availability of the NGINX web server.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eUpgrade NGINX Open Source and NGINX Plus to a patched version that addresses CVE-2026-27654 (consult the NGINX security advisories).\u003c/li\u003e\n\u003cli\u003eDisable the \u003ccode\u003engx_http_dav_module\u003c/code\u003e if it is not required for your web application.\u003c/li\u003e\n\u003cli\u003eIf the \u003ccode\u003engx_http_dav_module\u003c/code\u003e is necessary, carefully review and restrict the usage of MOVE and COPY methods, prefix locations, and alias directives in your NGINX configuration files.\u003c/li\u003e\n\u003cli\u003eDeploy the Sigma rule \u0026quot;Detect NGINX DAV Module Buffer Overflow Attempt\u0026quot; to your SIEM to identify potential exploitation attempts based on suspicious HTTP requests targeting DAV endpoints.\u003c/li\u003e\n\u003cli\u003eMonitor NGINX worker process stability and resource usage for unexpected crashes or high CPU utilization, which could indicate exploitation attempts.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2024-01-29T12:00:00Z","date_published":"2024-01-29T12:00:00Z","id":"https://feed.craftedsignal.io/briefs/2024-01-nginx-dav-overflow/","summary":"A buffer overflow vulnerability (CVE-2026-27654) exists in the ngx_http_dav_module of NGINX Open Source and NGINX Plus, potentially allowing attackers to terminate the NGINX worker process or modify files outside the document root by exploiting specific configurations with MOVE or COPY methods.","title":"NGINX ngx_http_dav_module Buffer Overflow Vulnerability (CVE-2026-27654)","url":"https://feed.craftedsignal.io/briefs/2024-01-nginx-dav-overflow/"}],"language":"en","title":"CraftedSignal Threat Feed - Dav","version":"https://jsonfeed.org/version/1.1"}