VulnerabilityPublished 24 Sep 2026Updated 29 Sep 2026

CVE-2026-61741: http4s-scala-xml · XML External Entity (XXE)

Affects http4s-scala-xmlSource CVE Database V5

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Not known to be exploited · CVSS 9.3 Critical : upgrade to 1.0.0-M39 or 0.24.1 as a priority.

Data as of 6 Nov 2026, 23:24 UTC

CVSS 3.1 base score

9.3Critical

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 22% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.0.0-M39, 0.24.1

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: High
Integrity: None
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: 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: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
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: None: There is no loss of integrity within 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 24 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 6 Nov 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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 http4s-scala-xml and http4s/http4s-scala-xml to 1.0.0-M39 or 0.24.1.

Affected software

Product	Affected	Fixed in
http4shttp4s-scala-xml	Affected >=1.0.0-M1 <1.0.0-M39	Fixed in 1.0.0-M39
http4shttp4s-scala-xml	Affected <0.24.1	Fixed in 0.24.1
GitHubhttp4s/http4s-scala-xml`pkg:github/http4s/http4s-scala-xml`Other threats	Affected <0.24.1 >=1.0.0-M1 <1.0.0-M39	Fixed in 0.24.1 1.0.0-M39

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

AI-suggested

Upgrade to http4s-scala-xml version 0.24.1 or later, or 1.0.0-M39 or later, where the XML parser is properly configured to disable external entity resolution and prevent XXE attacks. No other mitigation is required if these versions are in use.

Description

http4s-scala-xml provides `EntityDecoder[F, scala.xml.Elem]` instances that parse XML message bodies. Prior to versions 0.24.1 and 1.0.0-M39, these decoders used a `javax.xml.parsers.SAXParserFactory` obtained from `SAXParserFactory.newInstance` without any security configuration. With the JDK's default settings, the parser resolves DOCTYPE declarations, external general and parameter entities, and external DTDs.An application that uses these decoders to parse untrusted XML is vulnerable to XML External Entity (XXE) attacks. An attacker can craft a request that discloses local files readable by the service process, performs server-side request forgery (SSRF) against internal network resources, and/or causes denial of service through entity expansion. Versions 0.24.1 and 1.0.0-M39 fix the issue.

Impact

An attacker can exploit this vulnerability to read local files accessible by the service process, perform SSRF attacks against internal network resources, and cause denial of service conditions through XML entity expansion. The CVSS v3.1 score of 9.3 reflects a critical severity with network attack vector, low attack complexity, no privileges required, no user interaction, and high confidentiality impact but no integrity impact and low availability impact.

Summary

The http4s-scala-xml library provides XML decoders that use a SAXParserFactory instance without security configurations that disable external entity resolution. This improper restriction of XML External Entity references (CWE-611) allows attackers to craft malicious XML payloads that can lead to disclosure of local files, server-side request forgery (SSRF), and denial of service through entity expansion. The vulnerability affects versions prior to 0.24.1 and versions from 1.0.0-M1 up to but not including 1.0.0-M39. The issue is fixed in versions 0.24.1 and 1.0.0-M39.

CWE-611Improper Restriction of XML External Entity Reference (opens in a new tab)
Base weaknessOWASP Top 10 A02:2025: Security Misconfiguration (opens in a new tab)
The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.
Implementation · System Configuration
Many XML parsers and validators can be configured to disable external entity expansion.
OWASP Cheat Sheets
Deserialization (opens in a new tab)
XML Security (opens in a new tab)
XML External Entity Prevention (opens in a new tab)
OWASP ASVS 4.0.3
V5.5.2 (opens in a new tab)
Attack patterns
Data Serialization External Entities Blowup (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

github.com/http4s/http4s-scala-xml/security/advisories/GHSA-cjx3-73hr-rpw7 (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 2 Oct 2026, 16:49 UTC

WeaknessesCWE-611

Technical details

References

Community reviews

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