erroneo.us
Search all guides⌘K

Security Digest · Vulnerability record

CVE-2026-44990: Apostrophe has default XSS via `xmp` raw-text passthrough in `sanitize-html`

ApostropheCMS is an open-source Node.js content management system, and sanitize-html provides a simple HTML sanitizer with a clear API.

CVSS 9.3 Critical EPSS 0.7% · p52

Updated By erroneo.us Security Desk36 references Seen in the digest for May 14, 2026

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

  • Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
  • EPSS 0.7%, percentile 52: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 52% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
  • Needs a user to click or open something. Phishing makes that realistic, but it is not wormable.
  • Only applies if your dependency tree includes sanitize-html (npm) = 2.17.3, fixed in 2.17.4. Check your lockfile, including transitive dependencies.

What it is

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.

From the GitHub advisory

Summary Under the default configuration, sanitize-html 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.

Details In sanitize-html@2.17.3, the default nonTextTags list includes only script, style, textarea, and option in index.js lines 138-142. That means disallowed xmp tags are not treated as "drop the entire contents" tags.

Later, in the ontext handler at index.js lines 569-577, the code special-cases textarea and xmp and appends their text content directly to the output without escaping:

Because htmlparser2 treats xmp as a raw-text element, markup inside xmp is parsed as text on input but becomes live markup again once it is appended unescaped to the sanitized output.

This creates a default sanitizer bypass. For example, a disallowed wrapper can be used to smuggle or event-handler payloads through sanitization.

Weakness type: CWE-79.

Product: sanitize-html (npm) · Assigned by: GitHub_M · Published: 2026-06-12

Affected and fixed versions

EcosystemPackageVulnerableFirst fixed
npmsanitize-html= 2.17.32.17.4
VendorProductAffected versions (per CVE record)
apostrophecmssanitize-html< 2.17.4

Severity scores

Scored byCVSSScoreVector
GitHub_M3.19.3 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
redhat-SADP3.18.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
GitHub3.19.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
  • Attack vector: network (remotely reachable)
  • Attack complexity: low
  • Privileges required: none (no login)
  • User interaction: required (a user must click/open something)
  • Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

  • CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
  • CISA SSVC assessment: exploitation poc, automatable no, technical impact total.
  • FIRST EPSS (model of 2026-10-21): 0.69% probability of exploitation activity in the next 30 days; percentile 52.

Timeline

  • — GitHub-reviewed advisory GHSA-rpr9-rxv7-x643 published (critical)
  • — CVE record published by GitHub_M
  • — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

  1. access.redhat.com access.redhat.com
  2. access.redhat.com access.redhat.com
  3. access.redhat.com access.redhat.com
  4. access.redhat.com access.redhat.com
  5. access.redhat.com access.redhat.com
  6. access.redhat.com access.redhat.com
  7. access.redhat.com access.redhat.com
  8. access.redhat.com access.redhat.com
  9. access.redhat.com access.redhat.com
  10. access.redhat.com access.redhat.com
  11. access.redhat.com access.redhat.com
  12. access.redhat.com access.redhat.com
  13. access.redhat.com access.redhat.com
  14. access.redhat.com access.redhat.com
  15. access.redhat.com access.redhat.com
  16. access.redhat.com access.redhat.com
  17. access.redhat.com access.redhat.com
  18. access.redhat.com access.redhat.com
  19. access.redhat.com access.redhat.com
  20. access.redhat.com access.redhat.com
  21. access.redhat.com access.redhat.com
  22. access.redhat.com access.redhat.com
  23. access.redhat.com access.redhat.com
  24. access.redhat.com access.redhat.com
  25. access.redhat.com access.redhat.com
  26. access.redhat.com access.redhat.com
  27. access.redhat.com access.redhat.com

Vulnerability records

  1. GitHub Advisory GHSA-rpr9-rxv7-x643 github.com
  2. CVE.org record CVE-2026-44990 cve.org
  3. NVD entry CVE-2026-44990 nvd.nist.gov

Other references from the CVE record and advisory

  1. github.com github.com
  2. access.redhat.com access.redhat.com
  3. RHBZ#2488565 bugzilla.redhat.com
  4. security.access.redhat.com security.access.redhat.com
  5. github.com github.com
  6. github.com github.com

Critical npm advisories · Today’s Security Digest