sanitize-html: Improper Neutralization of Input During Web Page Generation
CVE-2026-44990 is a critical-severity improper neutralization of input during web page generation vulnerability in sanitize-html from Apostrophecms, with a CVSS 3.1 base score of 9.3 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. Affected sanitize-html versions: < 2.17.4. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.68% chance of exploitation within 30 days, higher than 53% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of sanitize-html 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.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
- 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; 5 further products are omitted here. 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
- NoneNo account or login is needed.
- 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
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N. Scored by CNA (github.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.3 | Critical | CNA (github.com) |
| CVSS 3.1 | 8.1 | High | CNA |
Official description
ApostropheCMS is an open-source Node.js content management system, and sanitize-html provides a simple HTML sanitizer with a clear API. Under the default configuration, versions of `sanitize-html` prior to 2.17.4 can turn attacker-controlled content inside a disallowed `xmp` element into live HTML or JavaScript. This is a sanitizer bypass in the default `disallowedTagsMode: 'discard'` path and can lead to stored XSS in applications that render sanitized output back to users. Version 2.17.4 patches the issue.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Input During Web Page Generation
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
How developers prevent this class of flaw
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples of libraries and frameworks that make it easier to generate properly encoded output include Microsoft's Anti-XSS library, the OWASP ESAPI Encoding module, and Apache Wicket.
- Understand all the potential areas where untrusted inputs can enter your software: 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.
- 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.
More Improper Neutralization of Input During Web Page Generation vulnerabilities (CWE-79)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
- access.redhat.com/errata/RHSA-2026:36882
- access.redhat.com/errata/RHSA-2026:36883
- access.redhat.com/errata/RHSA-2026:40262
- access.redhat.com/errata/RHSA-2026:41031
- access.redhat.com/errata/RHSA-2026:41055
- access.redhat.com/errata/RHSA-2026:41064
- access.redhat.com/errata/RHSA-2026:41066
- access.redhat.com/errata/RHSA-2026:42146
- access.redhat.com/errata/RHSA-2026:42796
- access.redhat.com/errata/RHSA-2026:43052
- access.redhat.com/errata/RHSA-2026:46598
- access.redhat.com/errata/RHSA-2026:46685
- access.redhat.com/errata/RHSA-2026:46885
- access.redhat.com/errata/RHSA-2026:46903
- access.redhat.com/errata/RHSA-2026:47735
Recent Improper Neutralization of Input During Web Page Generation vulnerabilities
- 8.7 High severity
- 7.3 High severity
- 7.1 High severity
- 8.1 High severity
- 8.7 High severity
- 8.7 High severity
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