CVE-2025-40908VulnerabilityPublished 1 Jun 2025

CVE-2025-40908: TINITA YAML::LibYAML · Exposed Files or Directories

Affects TINITA YAML::LibYAMLSource CVE Database V5

Not known to be exploited · CVSS 9.1 Critical · fixed in 0.903.0 : patch TINITA YAML::LibYAML as a priority.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

9.1Critical

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 39% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.903.0

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: None

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 1 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
TINITA YAML::LibYAML	Affected =0	Fixed in–

AI-suggested

European organizations should immediately audit their software dependencies to identify usage of YAML::LibYAML versions prior to 0.903.0. Where possible, upgrade to version 0.903.0 or later once available to ensure the vulnerability is patched. In the interim, restrict network exposure of services that utilize this library, especially those accepting YAML input from untrusted sources. Implement strict input validation and sanitization to prevent malicious YAML payloads from triggering file modifications. Employ file system access controls and mandatory access control (MAC) policies to limit the ability of processes to write to critical files, thereby reducing the impact of exploitation. Monitoring and alerting on unexpected file changes in directories used by YAML::LibYAML can help detect exploitation attempts early. Additionally, consider containerization or sandboxing of applications using this library to contain potential damage. Engage with vendors or maintainers for timely patch releases and apply them promptly. Finally, incorporate this vulnerability into incident response plans and conduct tabletop exercises simulating exploitation scenarios to improve readiness.

Description

YAML-LibYAML prior to 0.903.0 for Perl uses 2-args open, allowing existing files to be modified

Impact

For European organizations, the impact of CVE-2025-40908 can be significant, especially for those relying on Perl applications that utilize YAML::LibYAML for configuration management or data serialization. Unauthorized modification of YAML files could lead to compromised application configurations, leakage of sensitive information, or insertion of malicious data that could escalate into broader system compromise. Sectors such as finance, healthcare, government, and critical infrastructure, which often use Perl-based legacy systems or automation scripts, may face increased risks of data integrity breaches and operational disruptions. The remote exploitability without authentication or user interaction means attackers can potentially target exposed services or supply chain components that incorporate this library. Given the high confidentiality and integrity impact, organizations could suffer regulatory penalties under GDPR if personal data is exposed or altered. Additionally, the lack of availability impact suggests systems may continue running but with corrupted or maliciously altered data, complicating detection and response efforts.

CWE-552Files or Directories Accessible to External Parties (opens in a new tab)
Base weaknessOWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product makes files or directories accessible to unauthorized actors, even though they should not be.
Implementation · System Configuration · Operation
When storing data in the cloud (e.g., S3 buckets, Azure blobs, Google Cloud Storage, etc.), use the provider's controls to disable public access.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V12.5.1 (opens in a new tab)
V12.4.1 (opens in a new tab)
V8.3.8 (opens in a new tab)
Attack patterns
Collect Data from Common Resource Locations (opens in a new tab)
Probe System Files (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 9 Jul 2025, 00:57 UTC

WeaknessesCWE-552

Technical details

References

Community reviews

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