VulnerabilityPublished 10 Mar 2024Updated 15 Oct 2026

CVE-2024-28757: libexpat · XML Entity Expansion

Affects libexpatSource CVE Database V5

Not known to be exploited · CVSS 7.5 High : upgrade to 2.6.2 soon.

Data as of 26 Oct 2026, 09:15 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 2.0% chance of exploitation in 30 days – higher than 80% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.6.2

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
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: 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: 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 10 Mar 2024
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

Upgrade libexpat/libexpat to 2.6.2.

Affected software

Product	Affected	Fixed in
GitHublibexpat/libexpat`pkg:github/libexpat/libexpat`Other threats	Affected <2.6.2	Fixed in 2.6.2

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 audit their use of libexpat, focusing on whether XML_ExternalEntityParserCreate is used to create isolated external parsers. If so, they should avoid or disable this usage pattern until patches are available. Applying vendor patches or updates to libexpat once released is critical. In the interim, organizations can implement input validation and filtering to block XML documents containing external entity declarations or recursive entity references. Network-level protections such as Web Application Firewalls (WAFs) can be configured to detect and block malicious XML payloads exploiting entity expansion. Monitoring XML parser logs for unusual activity or resource spikes can provide early warning signs of exploitation attempts. For software vendors embedding libexpat, updating to a patched version and releasing updates to customers is essential. Additionally, organizations should consider isolating XML processing environments and applying resource limits to prevent resource exhaustion. Comprehensive incident response plans should be updated to include this vulnerability scenario.

Description

libexpat through 2.6.1 allows an XML Entity Expansion attack when there is isolated use of external parsers (created via XML_ExternalEntityParserCreate).

Impact

For European organizations, the primary impact of CVE-2024-28757 is the risk of denial of service attacks that can disrupt critical services relying on XML parsing. Industries such as telecommunications, finance, government, and energy often use XML for configuration, data interchange, and communication protocols, making them vulnerable to service outages. The vulnerability could lead to system downtime, degraded performance, and potential cascading failures in interconnected systems. Since the attack requires no authentication or user interaction, attackers can remotely trigger the vulnerability, increasing the risk of widespread disruption. Organizations using libexpat in custom or third-party applications that parse XML with external entity parsers are particularly at risk. The impact on availability could affect business continuity, regulatory compliance (e.g., GDPR mandates on service availability), and trust in digital services. Although confidentiality and integrity are not directly compromised, the operational impact can be severe, especially in critical infrastructure sectors.

CWE-776Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion') (opens in a new tab)
Base weaknessLikelihood of exploit: MediumOWASP Top 10 A02:2025: Security Misconfiguration (opens in a new tab)
The product uses XML documents and allows their structure to be defined with a Document Type Definition (DTD), but it does not properly control the number of recursive definitions of entities.
Operation
If possible, prohibit the use of DTDs or use an XML parser that limits the expansion of recursive DTD entities.
Implementation
Before parsing XML files with associated DTDs, scan for recursive entity declarations and do not continue parsing potentially explosive content.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (opens in a new tab)
Attack patterns
Exponential Data Expansion (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 11 Nov 2025, 21:05 UTC

WeaknessesCWE-776

Technical details

References

Community reviews

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