CVE-2025-66578VulnerabilityPublished 9 Dec 2025

CVE-2025-66578: robrichards xmlseclibs · Uncaught Exception

Affects robrichards xmlseclibsSource CVE Database V5

Not known to be exploited · CVSS 6.0 Medium : upgrade to 3.1.4 when convenient.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

6.0Medium

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 15% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.1.4

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

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

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: High: The attacker is authorized with (i.e., requires) privileges that provide significant (e.g., administrative) control over the vulnerable component that could affect component-wide settings and files.
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: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
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 impacted component 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 impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 9 Dec 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 2026-10-25.

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

Upgrade robrichards/xmlseclibs to 3.1.4.

Affected software

Product	Affected	Fixed in
Packagistrobrichards/xmlseclibs`pkg:composer/robrichards/xmlseclibs`Other threats	Affected <3.1.4	Fixed in 3.1.4

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should immediately upgrade xmlseclibs to version 3.1.4 or later, which contains the official fix for this vulnerability. If upgrading is not immediately feasible, implement strict validation checks to treat any canonicalization failure—such as exceptions, nil, or empty outputs—as fatal errors that abort XML signature validation. Code audits should be conducted to ensure no silent acceptance of empty canonicalization results occurs. Additionally, restrict privileges to minimize the risk of high-privilege account compromise, and monitor XML processing logs for anomalies indicative of signature bypass attempts. Employ defense-in-depth by validating XML inputs at multiple layers and using alternative signature verification libraries where possible. Regularly update libxml2 to the latest secure versions to reduce underlying library risks. Finally, conduct penetration testing focused on XML signature validation to detect potential exploitation.

Description

xmlseclibs is a library written in PHP for working with XML Encryption and Signatures. Versions 3.1.3 contain an authentication bypass vulnerability due to a flaw in the libxml2 canonicalization process during document transformation. When libxml2’s canonicalization is invoked on an invalid XML input, it may return an empty string rather than a canonicalized node.xmlseclibs then proceeds to compute the DigestValue over this empty string, treating it as if canonicalization succeeded. This issue is fixed in version 3.1.4. Workarounds include treating canonicalization failures (exceptions or nil/empty outputs) as fatal and aborting validation, and/or adding explicit checks to reject when canonicalize returns nil/empty or raises errors.

Impact

For European organizations, this vulnerability can undermine the trustworthiness of XML-based authentication and encryption mechanisms, which are commonly used in web services, SAML assertions, and secure communications. An attacker exploiting this flaw could bypass signature verification, leading to unauthorized access, data tampering, or injection of malicious payloads. This threatens confidentiality by exposing sensitive data, integrity by allowing unauthorized modifications, and availability by potentially disrupting services dependent on XML validation. Sectors such as finance, government, healthcare, and critical infrastructure that rely on XML security standards are particularly vulnerable. Given the network attack vector and the requirement for high privileges, insider threats or compromised accounts could leverage this vulnerability to escalate attacks. The absence of user interaction lowers the barrier for automated exploitation once privileges are obtained. Failure to patch or implement mitigations could result in data breaches, regulatory non-compliance (e.g., GDPR), and operational disruptions.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 16 Dec 2025, 06:07 UTC

WeaknessesCWE-248

Technical details

References

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