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GHSA-c4w7-xm78-47vh CVE-2020-7774

Prototype Pollution in y18n

Critical npm
Severity
7.3 / 10
Critical · CVSS 3.1
Exploit chance (EPSS)
69.59%
Chance of exploitation in the next 30 days. Higher than 99.37% of scored vulnerabilities.
Known exploited
No
Not in CISA's catalog
Weakness
CWE-1321 Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
CWE-20 Improper Input Validation
CWE-915 Improperly Controlled Modification of Dynamically-Determined Object Attributes
Fix
3.2.2
Upgrade y18n to this version or later

Description

Overview

The npm package y18n before versions 3.2.2, 4.0.1, and 5.0.5 is vulnerable to Prototype Pollution.

POC

const y18n = require('y18n')();

y18n.setLocale('__proto__');
y18n.updateLocale({polluted: true});

console.log(polluted); // true

Recommendation

Upgrade to version 3.2.2, 4.0.1, 5.0.5 or later.

Affected versions

npm

PackageVulnerableFixed in
y18n
< 3.2.2
3.2.2
y18n
>= 4.0.0, < 4.0.1
4.0.1
y18n
>= 5.0.0, < 5.0.5
5.0.5

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.

y18n npm → 3.2.2

npm
npm install y18n@3.2.2
yarn
yarn add y18n@3.2.2
pnpm
pnpm add y18n@3.2.2

Severity breakdown

CVSS 3.1 7.3

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

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

Weakness

CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.

How to prevent it
  • Implementation: By freezing the object prototype first (for example, Object.freeze(Object.prototype)), modification of the prototype becomes impossible.
  • Architecture and Design: By blocking modifications of attributes that resolve to object prototype, such as proto or prototype, this weakness can be mitigated.
  • Implementation: When handling untrusted objects, validating using a schema can be used.
  • Implementation: By using an object without prototypes (via Object.create(null) ), adding object prototype attributes by accessing the prototype via the special attributes becomes impossible, mitigating this weakness.
  • Implementation: Map can be used instead of objects in most cases. If Map methods are used instead of object attributes, it is not possible to access the object prototype or modify it.

CWE-20: Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

How to prevent it
  • Architecture and Design: Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build "recognizers" for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses. [REF-1109] [REF-1110] [REF-1111]
  • Architecture and Design: Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
  • Architecture and Design, Implementation: Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.
  • Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
  • Architecture and Design: For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server. Even though client-side checks provide minimal benefits with respect to server-side security, they are still useful. First, they can support intrusion detection. If the server receives input that should have been rejected by the client, then it may be an indication of an attack. Second, client-side error-checking can provide helpful feedback to the user about the expectations for valid input. Third, there may be a reduction in server-side processing time for accidental input errors, although this is typically a small savings.
  • Implementation: When your application combines data from multiple sources, perform the validation after the sources have been combined. The individual data elements may pass the validation step but violate the intended restrictions after they have been combined.
  • Implementation: Be especially careful to validate all input when invoking code that crosses language boundaries, such as from an interpreted language to native code. This could create an unexpected interaction between the language boundaries. Ensure that you are not violating any of the expectations of the language with which you are interfacing. For example, even though Java may not be susceptible to buffer overflows, providing a large argument in a call to native code might trigger an overflow.
  • Implementation: Directly convert your input type into the expected data type, such as using a conversion function that translates a string into a number. After converting to the expected data type, ensure that the input's values fall within the expected range of allowable values and that multi-field consistencies are maintained.
  • Implementation: Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180, CWE-181). Make sure that your application does not inadvertently decode the same input twice (CWE-174). Such errors could be used to bypass allowlist schemes by introducing dangerous inputs after they have been checked. Use libraries such as the OWASP ESAPI Canonicalization control. Consider performing repeated canonicalization until your input does not change any more. This will avoid double-decoding and similar scenarios, but it might inadvertently modify inputs that are allowed to contain properly-encoded dangerous content.
  • Implementation: When exchanging data between components, ensure that both components are using the same character encoding. Ensure that the proper encoding is applied at each interface. Explicitly set the encoding you are using whenever the protocol allows you to do so.

CWE-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes

The product receives input from an upstream component that specifies multiple attributes, properties, or fields that are to be initialized or updated in an object, but it does not properly control which attributes can be modified.

How to prevent it
  • Implementation: If available, use features of the language or framework that allow specification of allowlists of attributes or fields that are allowed to be modified. If possible, prefer allowlists over denylists. For applications written with Ruby on Rails, use the attr_accessible (allowlist) or attr_protected (denylist) macros in each class that may be used in mass assignment.
  • Architecture and Design, Implementation: If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified.
  • Implementation: For any externally-influenced input, check the input against an allowlist of internal object attributes or fields that are allowed to be modified.
  • Implementation, Architecture and Design: Refactor the code so that object attributes or fields do not need to be dynamically identified, and only expose getter/setter functionality for the intended attributes.

References

Advisories

Packages

Other links

Timeline

  1. Published
  2. Last updated by the source
  3. Latest EPSS score
AdvisorySeverityWhy it's related
GHSA-6wvx-3r32-xmcg
Forge: Prototype Pollution in forge.http cookie handling via a malicious Set-Cookie
Medium Same weakness, CWE-1321
GHSA-7648-jmwf-vw7j
systeminformation has prototype pollution in `networkStats()` via the interface name
Medium Same weakness, CWE-1321
GHSA-m2m5-rw3w-cwmj
ApostropheCMS: Client-side Prototype Pollution in apos.http.parseQuery leading to DOM-based XSS against authenticated users
Medium Same weakness, CWE-1321
GHSA-j5rq-xfvr-p969
ApostropheCMS: Authenticated projection-exclusion prototype-member deletion in @apostrophecms/db-connect causes process-wide denial of service
High Same weakness, CWE-1321
GHSA-97rh-rhh2-7vjv
Payload: Remote Code Execution through first-register
High Same weakness, CWE-1321
GHSA-4q55-j62x-fr9h
devalue: Malformed null-prototype object keys bypass __proto__ rejection via property-key coercion
Medium Same weakness, CWE-1321
GHSA-x97p-jq2g-jp4f
Axios: Prototype Pollution Gadget in axios toFormData Options
High Same weakness, CWE-1321
GHSA-vh66-26gq-q6x8
Axios: Prototype pollution gadget in fetch adapter can alter outbound requests
Medium Same weakness, CWE-1321
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