Vulnerability · Published Aug 23, 2026 · Assigned by VulnCheck

CVE-2026-9769justhtml before 1.10.0 Denial of Service via deeply nested HTML

High 7.5

In plain English

A high-severity security flaw in justhtml from EmilStenstrom. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 27% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.3%top 72.8% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

justhtml through 1.9.1 (fixed in 1.10.0) is vulnerable to uncontrolled recursion leading to denial of service. During JustHTML() construction, TreeBuilder.finish() unconditionally calls _populate_selectedcontent(), which recursively traverses the DOM tree via _find_elements()/_find_element() without a depth bound. An attacker who can supply HTML for parsing can provide deeply nested elements (e.g., ~1000 nested <div> tags, roughly 11 KB) to exceed CPython's default recursion limit and trigger an unhandled RecursionError, which may abort parsing, fail requests, or terminate a worker/process depending on the host application's exception handling.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
PyPI	justhtml	1.10.0	GHSA-v7cf-c9rm-wm3j
PyPI	justhtml	1.10.0	PYSEC-2026-3854

Affected products (as reported)

Vendor	Product	Versions
EmilStenstrom	justhtml	0 – before 1.10.0

Weakness: CWE-674 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

GitHub Security Advisory (GHSA-v7cf-c9rm-wm3j) vendor-advisory
VulnCheck Advisory: justhtml before 1.10.0 Denial of Service via deeply nested HTML third-party-advisory