VulnerabilityPublished 18 Feb 2022Updated 30 May 2025

CVE-2022-25313: Expat · Uncontrolled Recursion

Source CVE Database V5

Not known to be exploited · CVSS 6.5 Medium : upgrade to 2.4.5 when convenient.

Data as of 26 Oct 2026, 16:39 UTC

CVSS 3.1 base score

6.5Medium

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

EPSS: 3.2% chance of exploitation in 30 days – higher than 88% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.4.5

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

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

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: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 18 Feb 2022
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 or the CVSS exploit maturity 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 libexpat/libexpat to 2.4.5.

Affected software

Product	Affected	Fixed in
GitHublibexpat/libexpat`pkg:github/libexpat/libexpat`Other threats	Affected <2.4.5	Fixed in 2.4.5

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 take the following specific mitigation steps: 1) Inventory and identify all software and systems that use libexpat for XML parsing, including embedded devices and third-party applications. 2) Upgrade libexpat to version 2.4.5 or later, where the vulnerability is fixed. If direct upgrades are not feasible, apply vendor patches or updates that include the fixed libexpat version. 3) Implement input validation and XML parsing restrictions, such as disabling DTD processing or limiting the maximum allowed nesting depth of XML elements, to prevent exploitation via maliciously crafted XML. 4) Employ application-layer firewalls or XML gateways that can detect and block suspicious XML payloads with excessive nesting or large DTDs. 5) Monitor application logs and network traffic for unusual XML processing errors or crashes that may indicate attempted exploitation. 6) Educate users and administrators about the risks of processing untrusted XML files and the importance of applying security updates promptly. 7) For critical systems, consider sandboxing XML parsing operations to contain potential DoS effects. These targeted measures go beyond generic patching advice by focusing on detection, prevention, and operational controls tailored to the nature of this vulnerability.

Description

In Expat (aka libexpat) before 2.4.5, an attacker can trigger stack exhaustion in build_model via a large nesting depth in the DTD element.

Impact

For European organizations, the primary impact of CVE-2022-25313 is the risk of denial-of-service attacks against applications and services that rely on vulnerable versions of libexpat for XML parsing. This can disrupt business operations, especially in sectors where XML is heavily used for data interchange, such as finance, telecommunications, government services, and industrial control systems. The DoS condition could lead to service outages, degraded performance, or application crashes, impacting availability and potentially causing operational downtime. Since the vulnerability requires user interaction (e.g., processing a crafted XML file or message), threat actors might exploit it via phishing emails, malicious uploads, or network-based XML payloads. Although no direct data breach or integrity compromise is indicated, the availability impact can indirectly affect compliance with regulations such as GDPR if services become unavailable or data processing is interrupted. Additionally, organizations relying on third-party software embedding libexpat may face challenges in identifying and patching affected components promptly. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits over time.

CWE-674Uncontrolled Recursion (opens in a new tab)
Class weakness
The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.
Implementation
Ensure that an end condition will be reached under all logic conditions. The end condition may include checking against the depth of recursion and exiting with an error if the recursion goes too deep. The complexity of the end condition contributes to the effectiveness of this action.
Implementation
Increase the stack size.
Attack patterns
Serialized Data with Nested Payloads (opens in a new tab)
Oversized Serialized Data Payloads (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 8 Jul 2025, 13:58 UTC

WeaknessesCWE-674

Technical details

References

Community reviews

Related threats