Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:LSummary
CVE-2025-27219 is a medium-severity Allocation of Resources Without Limits or Throttling (CWE-770) vulnerability in Ruby-Lang Cgi. Its CVSS base score is 5.8 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Network Denial of Service (T1498); ranked in the top 46% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
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-2025-27219 is a Denial of Service (DoS) vulnerability in the CGI gem for Ruby versions before 0.4.2. Specifically, the CGI::Cookie.parse method in the CGI library fails to impose limits on the length of raw cookie values during parsing, allowing excessive resource consumption when processing extremely large cookies. This issue is cataloged under CWE-770 (Allocation of Resources Without Limits or Throttling) and carries a CVSS v3.1 base score of 5.8 (AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L).
The vulnerability can be exploited remotely by unauthenticated attackers with network access to a vulnerable Ruby application using the affected CGI gem. By sending HTTP requests containing oversized cookie values, an attacker can trigger high CPU or memory usage during parsing, leading to degraded performance or temporary service denial on the target system. No user interaction is required, and the low attack complexity makes it feasible for remote exploitation.
Advisories recommend upgrading to CGI gem version 0.4.2 or later to mitigate the issue, as documented in the ruby-advisory-db entry (https://github.com/rubysec/ruby-advisory-db/blob/master/gems/cgi/CVE-2025-27219.yml), the originating HackerOne report (https://hackerone.com/reports/2936778), and Debian LTS announcements (https://lists.debian.org/debian-lts-announce/2025/03/msg00008.html).
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-5556
Vulnerability Data
In the CGI gem before 0.4.2 for Ruby, the CGI::Cookie.parse method in the CGI library contains a potential Denial of Service (DoS) vulnerability. The method does not impose any limit on the length of the raw cookie value it processes.…
more
This oversight can lead to excessive resource consumption when parsing extremely large cookies.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
—
—
- 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