cal.diy: Improper Neutralization of Script-Related HTML Tags in a Web Page
CVE-2024-58353 is a high-severity improper neutralization of script-related HTML tags in a web page vulnerability in cal.diy from Calcom, with a CVSS 3.1 base score of 8.9 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, but only if a user takes part, for example by opening a link or file. Affected cal.diy versions: 4.7.15 and earlier. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.41% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of cal.diy you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- LowPerformance or availability is reduced.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L. Scored by CNA (vulncheck.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 9.3 | Critical | CNA (vulncheck.com) |
| CVSS 3.1 | 8.9 | High | CNA (vulncheck.com) |
Official description
Cal.com (repository calcom/cal.diy) in versions <= 4.7.15 is vulnerable to cross-site scripting (XSS) on the publicly accessible single booking view (e.g., /booking/<id>). Booking question (form field) labels are rendered via React's dangerouslySetInnerHTML without proper input sanitization or CSP, so an attacker who can create an event type with a malicious booking question label can inject arbitrary HTML/JavaScript that executes when a victim visits the booking view URL. Self-hosted instances with open registration are particularly at risk. The issue is fixed in version 4.7.16.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Script-Related HTML Tags in a Web Page
The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as <, >, and & that could be interpreted as web-scripting elements when they are sent to a downstream component that processes web pages.
How developers prevent this class of flaw
- With Struts, write all data from form beans with the bean's filter attribute set to true.
More Improper Neutralization of Script-Related HTML Tags in a Web Page vulnerabilities (CWE-80)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other vulnerabilities in cal.diy
- 10.0 Critical severity
- 8.9 High severity
- 9.9 Critical severity
Recent Improper Neutralization of Script-Related HTML Tags in a Web Page vulnerabilities
- 8.6 High severity
- 8.8 High severity
- 8.5 High severity
- 8.8 High severity
- 9.0 Critical severity
- 7.1 High severity
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