CVE-2026-45409
ADVISORY - githubSummary
This is the same issue as CVE-2024-3651, however the original remediation in 2024 was not a complete fix. 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.
Impact
A specially crafted argument to the idna.encode() function could consume significant resources. This may lead to a denial-of-service.
Patches
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).
Workarounds
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.
Common Weakness Enumeration (CWE)
Inefficient Regular Expression Complexity
GitHub
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CVSS SCORE
6.9medium| Package | Type | OS Name | OS Version | Affected Ranges | Fix Versions |
|---|---|---|---|---|---|
| idna | pypi | - | - | <3.15 | 3.15 |
CVSS:4 Severity and metrics
The CVSS metrics represent different qualitative aspects of a vulnerability that impact the overall score, as defined by the CVSS Specification.
The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone). One example of an Adjacent attack would be an ARP (IPv4) or neighbor discovery (IPv6) flood leading to a denial of service on the local LAN segment (e.g., CVE-2013-6014).
Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success when attacking the vulnerable component.
The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges.
There is no loss of confidentiality within the Vulnerable System.
There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
There is no loss of integrity within the Vulnerable System.
There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.