HTACG tidy-html5 parser.c InsertNodeAsParent null pointer dereference

published 2025-06-23 last yr. modified 2026-06-17 4mo ago also EUVD-2025-18857

cvss: 3.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.2%; EPSS 0.2% chance of exploitation in 30 days, percentile 5%
public exploits: 0; none known

A vulnerability was found in HTACG tidy-html5 5.8.0. It has been declared as problematic. This vulnerability affects the function InsertNodeAsParent of the file src/parser.c. The manipulation leads to null pointer dereference. Local access is required to approach this attack. The exploit has been disclosed to the public and may be used.

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CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: partial
Assessed: last yr. (2025-06-23)

Exploit prediction

0.17% chance of exploitation in the next 30 days, higher than 5% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

github.com https://github.com/user-attachments/files/19652942/tidy-html5_crash.txt referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	4.0	4.8	CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
CNA	3.1	3.3	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L/E:P/RL:X/RC:R
CNA	3.0	3.3	CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L/E:P/RL:X/RC:R
CNA	2.0	1.7	AV:L/AC:L/Au:S/C:N/I:N/A:P/E:POC/RL:ND/RC:UR
CNA	4.0	1.9	CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P/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
CNA	3.1	3.3	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
CNA	2.0	1.7	AV:L/AC:L/Au:S/C:N/I:N/A:P

Affected products

HTACG tidy-html5

Classification

Weakness

CWE-476 NULL Pointer Dereference
CWE-404 Improper Resource Shutdown or Release

References

github.com /user-attachments/files/19652942/tidy-html5_crash.txt
exploit
vuldb.com /?id.313612
vdb-entry, technical-description
vuldb.com /?ctiid.313612
signature, permissions-required
vuldb.com /?submit.601007
third-party-advisory
github.com /htacg/tidy-html5/issues/1141
issue-tracking

Sources

CVE List CVE-2025-6496
NVD CVE-2025-6496

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