GHSA-39q2-94rc-95cp
ADVISORY - githubSummary
Summary
In src/purify.ts:1117-1123, ADD_TAGS as a function (via EXTRA_ELEMENT_HANDLING.tagCheck) bypasses FORBID_TAGS due to short-circuit evaluation.
The condition:
!(tagCheck(tagName)) && (!ALLOWED_TAGS[tagName] || FORBID_TAGS[tagName])
When tagCheck(tagName) returns true, the entire condition is false and the element is kept — FORBID_TAGS[tagName] is never evaluated.
Inconsistency
This contradicts the attribute-side pattern at line 1214 where FORBID_ATTR explicitly wins first:
if (FORBID_ATTR[lcName]) { continue; }
For tags, FORBID should also take precedence over ADD.
Impact
Applications using both ADD_TAGS as a function and FORBID_TAGS simultaneously get unexpected behavior — forbidden tags are allowed through. Config-dependent but a genuine logic inconsistency.
Suggested Fix
Check FORBID_TAGS before tagCheck:
if (FORBID_TAGS[tagName]) { /* remove */ }
else if (tagCheck(tagName) || ALLOWED_TAGS[tagName]) { /* keep */ }
Affected Version
v3.3.3 (commit 883ac15)
Common Weakness Enumeration (CWE)
Operator Precedence Logic Error
GitHub
-
CVSS SCORE
5.3medium| Package | Type | OS Name | OS Version | Affected Ranges | Fix Versions |
|---|---|---|---|---|---|
| dompurify | npm | - | - | <=3.3.3 | 3.4.0 |
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.
Successful exploitation of this vulnerability requires limited interaction by the targeted user with the vulnerable system and the attacker's payload. These interactions would be considered involuntary and do not require that the user actively subvert protections built into the vulnerable system. Examples include: utilizing a website that has been modified to display malicious content when the page is rendered (most stored XSS or CSRF) running an application that calls a malicious binary that has been planted on the system using an application which generates traffic over an untrusted or compromised network (vulnerabilities requiring an on-path attacker).
There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Vulnerable System.
There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
There is no impact to availability within the Vulnerable System.
There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.