- Severity: MEDIUM
- CVE: CVE-2026-126351
- Ecosystems: rubygems
- Packages: addressable
### Impact
`Addressable::URI.normalize_path` takes time quadratic in the number of nested dot segments in a path (e.g., `”/” + “a/” * n + “../” * n`, which for n = 3 is `/a/a/a/../../../`), because it removes one dot segment per pass over the whole path. `URI#normalize`, `URI#normalized_path`, `URI#==`, `URI#===` and `URI#join` all call it. Normalizing, comparing or joining a URI taken from user input can result in uncontrolled resource consumption, leading to denial of service. On 2.9.0, normalizing a 34 KB path takes about 3.5 seconds on MRI Ruby 4.0, and the cost grows with the square of the path length.
This affects every Ruby implementation, including MRI Ruby 3.2 and later. `URI.parse` by itself is unaffected, as is code that never normalizes, compares, or joins URIs from untrusted sources.
### Affected Versions
This vulnerability affects all versions of Addressable prior to 2.9.1. It is fixed in 2.9.1.
### Workarounds
– Limit the length of URIs taken from user input before calling `normalize`, `==` or `join` on them. Web servers often limit request lines to about 8 KB, which keeps the cost to about 150 milliseconds per call on typical hardware, but URIs from other sources (request bodies, headers such as `Location`, stored data) may not be limited.
– Reject paths with many dot segments before normalizing them.
### Credits
Reported by Matthew Mongeau (@halogenandtoast), Ruby Central Gem Security, who also suggested the single-pass approach used in the fix.
###…
Source: GitHub Security Advisories · 2026-11-12