CVE-2026-35611
Addressable Project Addressable 2.3.0 – 2.9.0
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). EPSS scores by FIRST (EPSS SIG), generated by Empirical Security. Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-35611 is a high-severity Inefficient Regular Expression Complexity (CWE-1333) vulnerability in Addressable Project Addressable. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Endpoint Denial of Service (T1499); ranked at the 39th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-15 (Development Process, Standards, and Tools) — 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-2026-35611 affects the Addressable Ruby gem, an alternative implementation to Ruby's standard library URI handling, specifically in its URI template functionality. Versions from 2.3.0 up to but not including 2.9.0 contain two classes of vulnerabilities where generated regular expressions are susceptible to catastrophic backtracking. The first involves templates using the explode modifier (*) with any expansion operator, such as {foo*}, {+var*}, or {/var*}, which produce patterns with nested unbounded quantifiers exhibiting O(2^n) complexity. The second involves templates with multiple variables using the + or # operators, like {+v1,v2,v3}, resulting in O(n^k) complexity due to ambiguous backtracking across variables caused by the comma separator in the character class. Matching these patterns against maliciously crafted URIs leads to uncontrolled resource consumption and denial of service.
Attackers can exploit this vulnerability remotely over the network with low complexity and no privileges or user interaction required, as indicated by its CVSS 3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). Any application using the affected Addressable versions that processes untrusted URI templates—such as in web frameworks, APIs, or URL parsing libraries—could be targeted by sending a specially crafted URI that triggers the vulnerable regex during template expansion or validation, causing excessive CPU usage and potential service disruption.
The GitHub security advisory at https://github.com/sporkmonger/addressable/security/advisories/GHSA-h27x-rffw-24p4 confirms the issue and states that it is fixed in Addressable version 2.9.0, recommending immediate upgrades for affected users. This aligns with CWE-1333 (Inefficient Regular Expression Complexity).
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-19788
Vulnerability Data
Addressable is an alternative implementation to the URI implementation that is part of Ruby's standard library. From 2.3.0 to before 2.9.0, within the URI template implementation in Addressable, two classes of URI template generate regular expressions vulnerable to catastrophic backtracking.…
more
Templates using the * (explode) modifier with any expansion operator (e.g., {foo*}, {+var*}, {#var*}, {/var*}, {.var*}, {;var*}, {?var*}, {&var*}) generate patterns with nested unbounded quantifiers that are O(2^n) when matched against a maliciously crafted URI. Templates using multiple variables with the + or # operators (e.g., {+v1,v2,v3}) generate patterns with O(n^k) complexity due to the comma separator being within the matched character class, causing ambiguous backtracking across k variables. When matched against a maliciously crafted URI, this can result in catastrophic backtracking and uncontrolled resource consumption, leading to denial of service. This vulnerability is fixed in 2.9.0.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation can discover inefficient regex patterns via performance or static analysis.
Development standards and tools can require safe regex construction and forbid known exponential patterns.
Denial-of-service protections limit resource exhaustion caused by expensive regex evaluation.
Input validation can constrain data that would otherwise trigger worst-case regex complexity.
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.
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.
Security testing can detect and reject regex patterns with exponential worst-case complexity.
Secure coding standards explicitly prohibit or limit the use of inefficient regular expressions.