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GHSA-jjg7-2v4v-x38h CVE-2024-3651 PYSEC-2024-60

Internationalized Domain Names in Applications (IDNA) vulnerable to denial of service from specially crafted inputs to idna.encode

Medium PyPI
Severity
6.9 / 10
Medium · CVSS 4.0
Exploit chance (EPSS)
1.39%
Chance of exploitation in the next 30 days. Higher than 72.23% of scored vulnerabilities.
Known exploited
No
Not in CISA's catalog
Weakness
CWE-400 Uncontrolled Resource Consumption
CWE-1333 Inefficient Regular Expression Complexity
Fix
3.7
Upgrade idna to this version or later

Description

Impact

A specially crafted argument to the idna.encode() function could consume significant resources. This may lead to a denial-of-service.

Patches

The function has been refined to reject such strings without the associated resource consumption in version 3.7.

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.

References

Affected versions

PyPI

PackageVulnerableFixed in
idna
< 3.7
3.7
idna
< 3.7
3.7
idna
>= 0.1, < 3.7
3.7

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

idna PyPI → 3.7

pip
pip install --upgrade "idna>=3.7"
poetry
poetry add "idna>=3.7"
uv
uv add "idna>=3.7"

Severity breakdown

CVSS 4.0 6.9

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Attack vector
Local
Attack complexity
Low
Attack requirements
None
Privileges required
None
User interaction
None
Confidentiality (vulnerable system)
None
Integrity (vulnerable system)
None
Availability (vulnerable system)
High
Confidentiality (subsequent systems)
None
Integrity (subsequent systems)
None
Availability (subsequent systems)
None

CVSS 3.1 6.2

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Weakness

CWE-400: Uncontrolled Resource Consumption

The product does not properly control the allocation and maintenance of a limited resource.

How to prevent it
  • Architecture and Design: Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.
  • Architecture and Design: Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed. The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question. The second solution is simply difficult to effectively institute -- and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
  • Architecture and Design: Ensure that protocols have specific limits of scale placed on them.
  • Implementation: Ensure that all failures in resource allocation place the system into a safe posture.

CWE-1333: Inefficient Regular Expression Complexity

The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.

How to prevent it
  • Architecture and Design: Use regular expressions that do not support backtracking, e.g. by removing nested quantifiers.
  • System Configuration: Set backtracking limits in the configuration of the regular expression implementation, such as PHP's pcre.backtrack_limit. Also consider limits on execution time for the process.
  • Implementation: Do not use regular expressions with untrusted input. If regular expressions must be used, avoid using backtracking in the expression.
  • Implementation: Limit the length of the input that the regular expression will process.

References

Advisories

Fixes and patches

Packages

Other links

Timeline

  1. Published
  2. Last updated by the source
  3. Latest EPSS score
AdvisorySeverityWhy it's related
GHSA-65pc-fj4g-8rjx
Internationalized Domain Names in Applications (IDNA): Specially crafted inputs to idna.encode() can bypass CVE-2024-3651 fix
Medium Also affects idna
GHSA-cggf-277g-3q54
pypdf has possible large memory usage when parsing page tree
High Same weakness, CWE-400
GHSA-3g3m-2fjr-6pw4
Glob: AbortSignal cancellation bypass allows post-timeout filesystem traversal
Medium Same weakness, CWE-400
GHSA-42gh-23hr-vphw
pypdf has possible long runtimes when retrieving page labels
High Same weakness, CWE-400
GHSA-4vqv-7265-gm2w
pypdf has possible large memory usage for exceptions in strict mode
High Same weakness, CWE-400
GHSA-62m5-6wh8-28x7
pypdf has possible long runtimes/large memory usage for encrypted PDF files
High Same weakness, CWE-400
GHSA-7wch-p9px-956x
Forge: Regular expression denial of service in PEM decoding (pem.decode)
High Same weakness, CWE-400
GHSA-fw5c-8223-6h42
russh: peer-declared zero maximum packet size permanently stalls channel writes (silent AsyncWrite hang)
Medium Same weakness, CWE-400

Credits: guidovranken

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