CVE-2025-12084VulnerabilityPublished 3 Dec 2025Updated 3 Mar 2026

CVE-2025-12084: Python Software Foundation CPython · Vulnerability

Affects Python Software Foundation CPythonSource CVE Database V5

Not known to be exploited · CVSS 6.3 Medium.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 4.0 base score

6.3Medium

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

EPSS: 0.7% chance of exploitation in 30 days – higher than 56% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: Present
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

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

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, 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: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: Present: The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: a race condition must be won to successfully exploit the vulnerability (the successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker, or the attack may need to be launched multiple times against a single target before being successful); the attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system 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 Vulnerable System 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 Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 3 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

Affected software

Product	Affected	Fixed in
GitHubpython/cpython`pkg:github/python/cpython`Other threats	Affected =0 =3.11.0 =3.12.0 =3.13.0 =3.14.0 =3.15.0	Fixed in–

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

AI-suggested

To mitigate CVE-2025-12084, organizations should implement several specific measures beyond generic advice: 1) Monitor and restrict the complexity and depth of XML documents accepted by applications using xml.dom.minidom, employing XML schema validation or custom logic to reject excessively nested structures. 2) Where feasible, replace xml.dom.minidom with more efficient XML parsing libraries that do not exhibit quadratic behavior or that provide built-in protections against deeply nested XML. 3) Implement resource usage limits (CPU and memory) on processes handling XML parsing to contain potential denial of service impacts. 4) Employ network-level protections such as rate limiting and input validation to reduce exposure to crafted XML payloads. 5) Stay alert for official patches or updates from the Python Software Foundation and apply them promptly once available. 6) In environments processing untrusted XML, consider sandboxing or isolating XML parsing components to minimize the blast radius of potential DoS attacks. 7) Conduct code reviews and testing focused on XML handling to identify and remediate similar inefficiencies or vulnerabilities.

Description

When building nested elements using xml.dom.minidom methods such as appendChild() that have a dependency on _clear_id_cache() the algorithm is quadratic. Availability can be impacted when building excessively nested documents.

Impact

The primary impact of CVE-2025-12084 is on system availability due to potential denial of service caused by excessive CPU consumption when processing deeply nested XML documents. Organizations that utilize CPython's xml.dom.minidom module to parse or build XML data—especially from untrusted sources—are at risk of service disruption. This can affect web servers, APIs, automated data processing pipelines, and any application relying on XML parsing. The vulnerability does not compromise confidentiality or integrity, but availability degradation can lead to downtime, reduced reliability, and potential cascading failures in dependent systems. The ease of exploitation (no authentication or user interaction required) and network accessibility increase the risk profile. However, the lack of known exploits in the wild and the medium CVSS score suggest that while impactful, the threat is moderate and manageable with proper controls. Organizations with high XML processing loads or exposed XML interfaces are particularly vulnerable, and denial of service attacks could be used as part of broader attack campaigns or to disrupt critical services.

CWE-407Inefficient Algorithmic Complexity (opens in a new tab)
Class weaknessLikelihood of exploit: Low
An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (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 3 Mar 2026, 18:31 UTC

WeaknessesCWE-407

Technical details

References

Community reviews

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