{"cve":"CVE-2026-45409","nvd":{"published":"2026-06-05T23:16:43.343","modified":"2026-07-23T07:10:00.113","status":"Analyzed","description":"Internationalized Domain Names in Applications (IDNA) for Python provides support for Internationalized Domain Names in Applications (IDNA) and Unicode IDNA Compatibility Processing. In versions prior to 3.15, payloads such as `\"\\u0660\" * N` or `\"\\u30fb\" * N + \"\\u6f22\"` utilize the `valid_contexto` function prior to length rejection, and for high values of `N` will take a long time to process. This is the same issue as CVE-2024-3651, however the original remediation in 2024 was not a complete fix. A specially crafted argument to the `idna.encode()` function could consume significant resources. This may lead to a denial-of-service. Starting in version 3.14, the function rejects long inputs as soon as practicable prior to any further processing to minimize resource consumption. In version 3.15, this approach was extended to lesser used alternate functions (i.e. per-label conversions and codec support). A workaround is available. Domain names cannot exceed 253 characters in length. If this length limit is enforced prior to passing the domain to the `idna.encode()` function, it should no longer consume significant resources. This is triggered by arbitrarily large inputs that would not occur in normal usage, but may be passed to the library assuming there is no preliminary input validation by the higher-level application.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N","score":6.9},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","score":5.3},"cwes":["CWE-1333"],"references":["https://github.com/kjd/idna/security/advisories/GHSA-65pc-fj4g-8rjx"],"products":["kjd:internationalized_domain_names_in_applications"],"source":"nvd","synced_at":"2026-10-19T22:37:48.043517290+00:00"},"epss":{"cve":"CVE-2026-45409","score":0.00408,"percentile":0.351,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-65pc-fj4g-8rjx","url":"https://osv.dev/vulnerability/GHSA-65pc-fj4g-8rjx","summary":"Internationalized Domain Names in Applications (IDNA): Specially crafted inputs to idna.encode() can bypass CVE-2024-3651 fix","modified":"2026-09-10T03:50:45.700124422Z","packages":[{"ecosystem":"PyPI","name":"idna","purl":"pkg:pypi/idna","ranges":["<3.15"],"fixed":["3.15"]}]},{"id":"PYSEC-2026-215","url":"https://osv.dev/vulnerability/PYSEC-2026-215","summary":"","modified":"2026-06-16T16:15:04.639265054Z","packages":[{"ecosystem":"PyPI","name":"idna","purl":"pkg:pypi/idna","ranges":["<3.15"],"fixed":["3.15"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}