CVE-2025-6498VulnerabilityPublished 23 Jun 2025

CVE-2025-6498: HTACG tidy-html5 · Memory Leak

Affects HTACG tidy-html5Source CVE Database V5

Not known to be exploited · CVSS 4.8 Medium.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 4.0 base score

4.8Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 14% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Base metrics

Attack Vector: Local
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Threat metrics

Exploit Maturity: POC

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.
Exploit Maturity: POC: Based on threat intelligence sources each of the following must apply: · Proof-of-concept is publicly available · No knowledge of reported attempts to exploit this vulnerability · No knowledge of publicly available solutions used to simplify attempts to exploit the vulnerability

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 23 Jun 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
GitHubhtacg/tidy-html5`pkg:github/htacg/tidy-html5`Other threats	Affected =5.8.0	Fixed in–

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AI-suggested

1. Monitor memory usage closely on systems running tidy-html5 5.8.0, especially on servers processing large volumes of HTML content or running continuous integration pipelines. 2. Restrict local access to trusted users only, minimizing the risk of local exploitation. 3. Implement resource limits (e.g., cgroups on Linux) on processes invoking tidy-html5 to prevent excessive memory consumption from impacting other services. 4. Where feasible, replace or isolate the use of tidy-html5 5.8.0 in critical environments until a patched version is available. 5. Employ containerization or sandboxing techniques to limit the impact of potential memory leaks. 6. Stay updated with HTACG project releases and apply patches promptly once available. 7. Conduct regular code audits and testing on HTML processing workflows to detect abnormal resource usage early. 8. Educate local users and administrators about the vulnerability to prevent inadvertent exploitation or misuse.

Description

A vulnerability classified as problematic has been found in HTACG tidy-html5 5.8.0. Affected is the function defaultAlloc of the file src/alloc.c. The manipulation leads to memory leak. It is possible to launch the attack on the local host. The exploit has been disclosed to the public and may be used.

Impact

For European organizations, the impact of CVE-2025-6498 is primarily related to system stability and availability. Organizations that integrate tidy-html5 5.8.0 into their development pipelines, content management systems, or automated HTML processing tools may experience degraded performance or service interruptions due to memory exhaustion caused by the leak. This could affect web hosting providers, digital agencies, and enterprises relying on automated HTML validation or cleanup. While the vulnerability does not directly compromise data confidentiality or integrity, prolonged exploitation could lead to denial of service conditions, impacting business continuity. Given the local attack vector, the threat is more significant in environments where multiple users have local access or where attackers can gain local footholds, such as shared hosting or development servers. The absence of known active exploits reduces immediate risk, but public disclosure increases the likelihood of future exploitation attempts. European organizations with strict uptime requirements or limited monitoring of memory usage may face operational disruptions. Additionally, sectors with high regulatory compliance demands (e.g., finance, healthcare) may be indirectly impacted if service availability is compromised.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 23 Jun 2025, 02:04 UTC

Technical details

References

Community reviews

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