CVE-2025-6494VulnerabilityPublished 22 Jun 2025Updated 30 Jun 2025

CVE-2025-6494: sparklemotion nokogiri · Heap-based Buffer Overflow

Affects sparklemotion nokogiriSource CVE Database V5

Not known to be exploited · CVSS 4.8 Medium.

Data as of 26 Oct 2026, 08:30 UTC

CVSS 4.0 base score

4.8Medium

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

EPSS: 0.1% chance of exploitation in 30 days – higher than 7% 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 22 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 26 Oct 2026.

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

AI-suggested

Immediately restrict local access to systems running vulnerable Nokogiri versions to trusted personnel only.

Implement strict user privilege management and enforce the principle of least privilege to minimize the risk of local exploitation.

Monitor local system logs and application behavior for anomalies indicative of exploitation attempts, such as unexpected crashes or memory errors in Nokogiri-dependent applications.

Where possible, isolate development and build environments to prevent untrusted code execution on systems with Nokogiri installed.

Apply virtual patching or runtime application self-protection (RASP) techniques to detect and block suspicious calls to the vulnerable hashmap_get_with_hash function until an official patch is released.

Engage with the Nokogiri maintainers or community to obtain updates or patches as soon as they become available and plan prompt deployment.

Conduct internal audits to identify all instances of Nokogiri usage across the organization, including embedded or indirect dependencies, to ensure comprehensive coverage.

Educate developers and system administrators about the vulnerability and the importance of local system security hygiene.

Description

A vulnerability was found in sparklemotion nokogiri c29c920907366cb74af13b4dc2230e9c9e23b833. It has been classified as problematic. This affects the function hashmap_get_with_hash of the file gumbo-parser/src/hashmap.c. The manipulation leads to heap-based buffer overflow. An attack has to be approached locally. The exploit has been disclosed to the public and may be used. The real existence of this vulnerability is still doubted at the moment. The patch is named ada4708e5a67114402cd3feb70a4e1d1d7cf773a. It is recommended to apply a patch to fix this issue. The project maintainer explains that the affected code was merged into the main branch but the commit never appeared in an official release.

Impact

For European organizations, the impact of CVE-2025-6494 is primarily relevant in environments where Nokogiri is used in local processing contexts, such as development workstations, CI/CD pipelines, or internal automation tools. Since the vulnerability requires local access, the risk is higher in organizations with large developer teams, shared workstations, or environments where untrusted users have local system access. Exploitation could lead to application crashes or arbitrary code execution, potentially allowing attackers to escalate privileges or move laterally within internal networks. This could disrupt business operations, compromise sensitive data processed locally, or undermine the integrity of software development processes. Sectors with high reliance on Ruby-based applications, such as financial services, technology firms, and research institutions, may face elevated risks. The medium severity rating suggests that while the vulnerability is not critical, it should not be ignored, especially in environments with lax local access controls. The lack of known exploits in the wild reduces immediate threat levels but does not preclude future attacks. European organizations must consider the potential for insider threats or compromised local accounts to leverage this vulnerability.

Summary

CVE-2025-6494 is a heap-based buffer overflow vulnerability identified in the Nokogiri library, specifically affecting versions 1.18.0 through 1.18.7. Nokogiri is a widely used Ruby gem for parsing HTML, XML, and other markup languages, leveraging the Gumbo parser internally. The vulnerability resides in the function hashmap_get_with_hash within the file gumbo-parser/src/hashmap.c. This function is responsible for retrieving elements from a hashmap data structure, and improper handling of input data leads to a heap-based buffer overflow condition. Such a flaw can cause memory corruption, potentially allowing an attacker to execute arbitrary code or cause a denial of service by crashing the application. The vulnerability requires local access with low privileges (PR:L) and does not require user interaction (UI:N). The attack complexity is low (AC:L), and no authentication is needed (AT:N). The CVSS v4.0 base score is 4.8, categorizing it as a medium severity issue. Although the exploit has been publicly disclosed, there are no known exploits in the wild at the time of publication. The vulnerability affects only local attackers who can execute code on the target system, which limits the attack surface. However, given Nokogiri's widespread use in web applications, development tools, and automation scripts, the risk remains significant in environments where untrusted local code execution is possible. The vulnerability does not impact confidentiality, integrity, or availability directly over a network, but local exploitation could lead to privilege escalation or application crashes. No official patches or updates have been linked yet, so mitigation relies on restricting local access and monitoring for suspicious activity.

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 22 Jun 2025, 23:04 UTC

Technical details

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