CVE-2026-9769 json
justhtml before 1.10.0 Denial of Service via deeply nested HTML
published 7mo ago modified 30d ago also GHSA-v7cf-c9rm-wm3j , PYSEC-2026-3854 , EUVD-2026-64661
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 27%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- pypi justhtml 1.10.0
- EmilStenstrom justhtml 1.10.0
Is CVE-2026-9769 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 2mo ago
Exploit prediction
0.34% chance of exploitation in the next 30 days, higher than 27% of all scored CVEs (FIRST EPSS, 2026-11-11).
Exploits and checks
- github.com https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-v7cf-c9rm-wm3j referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 8.7 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N |
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| CNA | 4.0 | 8.7 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | justhtml | <1.10.0 |
1.10.0 |
Affected products
- EmilStenstrom justhtml
Classification
- Weakness
-
- CWE-674 Uncontrolled Recursion
References
-
github.com
/EmilStenstrom/justhtml/security/advisories/GHSA-v7cf-c9rm-wm3j
vendor-advisory, exploit, web
-
vulncheck.com
/advisories/justhtml-before-denial-of-service-via-deeply-nested-html
third-party-advisory, web
-
nvd.nist.gov
/vuln/detail/CVE-2026-9769
advisory
-
github.com
/EmilStenstrom/justhtml
package
-
github.com
/EmilStenstrom/justhtml/releases/tag/v1.10.0
web
-
pypi.org
/project/justhtml
package
-
github.com
/advisories/GHSA-v7cf-c9rm-wm3j
advisory
Sources
- CVE List CVE-2026-9769
- GitHub Advisory GHSA-v7cf-c9rm-wm3j
- NVD CVE-2026-9769
- OSV PYSEC-2026-3854
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.