Raw vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HSummary
CVE-2026-27729 is a medium-severity Allocation of Resources Without Limits or Throttling (CWE-770) vulnerability in Astro \@Astrojs\/Node. Its CVSS base score is 5.9 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Network Denial of Service (T1498); ranked at the 34th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to AC-10 (Concurrent Session Control) and SC-6 (Resource Availability) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-27729 affects the Astro web framework in versions 9.0.0 through 9.5.3, specifically server actions in on-demand rendered sites using the Node adapter in standalone mode. The vulnerability stems from a lack of default request body size limits when parsing incoming JSON or FormData bodies, which are fully buffered into memory. This enables memory exhaustion denial-of-service (DoS) attacks, as a single oversized POST request to a valid server action endpoint can exhaust the process heap and crash the server, particularly on memory-constrained deployments.
Unauthenticated remote attackers can exploit this by discovering action names from HTML form attributes on public pages and sending oversized POST requests to those endpoints. A single request crashes the server process, while repeated requests in containerized environments trigger a persistent crash-restart loop, rendering the service unavailable. The CVSS v3.1 base score is 5.9 (AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H), reflecting network accessibility with high attack complexity but no privileges required and high availability impact.
Mitigation is available in Astro version 9.5.4, which introduces a fix for the missing body size limit. Relevant advisories and resources include the GitHub security advisory (GHSA-jm64-8m5q-4qh8), the fixing commit (522f880b07a4ea7d69a19b5507fb53a5ed6c87f8), pull request #15564, and the release notes for @astrojs/node@9.5.4. Security practitioners should upgrade SSR standalone deployments to the patched version and review public forms for exposed action endpoints.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-7451
Vulnerability Data
Astro is a web framework. In versions 9.0.0 through 9.5.3, Astro server actions have no default request body size limit, which can lead to memory exhaustion DoS. A single large POST to a valid action endpoint can crash the server…
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process on memory-constrained deployments. On-demand rendered sites built with Astro can define server actions, which automatically parse incoming request bodies (JSON or FormData). The body is buffered entirely into memory with no size limit — a single oversized request is sufficient to exhaust the process heap and crash the server. Astro's Node adapter (`mode: 'standalone'`) creates an HTTP server with no body size protection. In containerized environments, the crashed process is automatically restarted, and repeated requests cause a persistent crash-restart loop. Action names are discoverable from HTML form attributes on any public page, so no authentication is required. The vulnerability allows unauthenticated denial of service against SSR standalone deployments using server actions. A single oversized request crashes the server process, and repeated requests cause a persistent crash-restart loop in containerized environments. Version 9.5.4 contains a fix.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 5 hardening rules · 3 OS baselines
V15.4.4
Mitigating Controls (NIST 800-53 r5) AI
Directly enforces a hard limit on concurrent sessions, structurally preventing unbounded resource allocation.
Requires explicit allocation of resources by priority or quota, directly stopping unlimited allocation.
Imposes a limit on consecutive invalid attempts, preventing one specific class of unbounded resource consumption.
Reduces impact of resulting DoS events without preventing the underlying lack of allocation limits.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Monitoring capacity and taking action to maintain availability directly reduces unchecked resource allocation.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Baseline comparison of CPU, memory and bandwidth usage helps surface uncontrolled resource allocations before they cause service degradation.
Capacity projections and elasticity measures ensure that allocation requests are bounded and can be throttled, reducing the window in which an attacker can force unbounded resource reservations.
Defining retention periods and deletion schedules for backup copies prevents indefinite accumulation of data on storage media without corresponding resource-management controls.
Architectural redundancy and automatic failover limit the impact of an attacker who forces excessive allocations, because spare capacity can absorb the load until the primary instance recovers.
Documented incident response procedures that include activation of continuity plans and controlled recovery help ensure that resource consumption triggered by an incident is bounded and managed rather than left unbounded.
Mandating tested continuity procedures that preserve or replace resource-limiting controls prevents an attacker from exploiting the absence of throttling mechanisms during an outage.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (2 rules)
- V-248552 OL 8 must be configured so that all network connections associated with SSH traffic terminate after becoming unresponsive. prevents CWE-770
- V-248553 OL 8 must be configured so that all network connections associated with SSH traffic are terminated after 10 minutes of becoming unresponsive. prevents CWE-770
Oracle Linux 9 (2 rules)
- V-271710 OL 9 must be configured so that all network connections associated with SSH traffic are terminated after 10 minutes of becoming unresponsive. prevents CWE-770
- V-271709 OL 9 must be configured so that all network connections associated with SSH traffic terminate after becoming unresponsive. prevents CWE-770
RHEL 8 (1 rule)
- V-230244 RHEL 8 must be configured so that all network connections associated with SSH traffic terminate after becoming unresponsive. prevents CWE-770