CVE-2025-13837VulnerabilityPublished 1 Dec 2025Updated 3 Mar 2026

CVE-2025-13837: Python Software Foundation CPython · Vulnerability

Affects Python Software Foundation CPythonSource CVE Database V5

Not known to be exploited · CVSS 2.1 Medium.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 4.0 base score

2.1Medium

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 12% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Local
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: Low
Subsequent system availability: None

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

Attack Vector: Local: The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
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: 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 to the Subsequent 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 1 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-2025-13837, organizations should implement the following specific measures: 1) Avoid parsing plist files from untrusted or unauthenticated sources whenever possible. 2) Implement input validation and size checks before passing plist files to the plistlib module, ensuring that size fields are within reasonable bounds to prevent excessive memory allocation. 3) Employ resource limits at the operating system or container level (e.g., cgroups, ulimit) to restrict memory usage of Python processes, mitigating the impact of potential OOM conditions. 4) Monitor Python application logs and system resource usage for signs of abnormal memory consumption or crashes related to plist parsing. 5) Stay updated with Python Software Foundation releases and apply patches promptly once available. 6) Consider sandboxing or isolating processes that handle plist files to contain potential denial of service effects. 7) For developers, review and contribute to the plistlib module code to add robust size validation and error handling to prevent similar issues in future versions. These targeted actions go beyond generic advice by focusing on controlling input size, resource constraints, and proactive monitoring specific to plist parsing.

Description

When loading a plist file, the plistlib module reads data in size specified by the file itself, meaning a malicious file can cause OOM and DoS issues

Impact

The primary impact of CVE-2025-13837 is denial of service through resource exhaustion. Organizations running Python applications that parse plist files using the vulnerable plistlib module may experience crashes or service interruptions if exposed to malicious plist files. This can affect backend services, automation scripts, or desktop applications that rely on plist parsing. While the vulnerability does not directly compromise confidentiality or integrity, the resulting denial of service can disrupt business operations, degrade user experience, and potentially cause cascading failures in dependent systems. Since exploitation requires local access to supply the malicious file, remote exploitation is unlikely unless combined with other vulnerabilities or misconfigurations. The impact is more significant in environments where plist files are received from untrusted sources or where automated processing of plist files occurs without validation. Given the widespread use of Python globally, especially in development, automation, and system management, the vulnerability has broad potential reach but limited severity due to exploitation constraints.

Summary

CVE-2025-13837 identifies a resource exhaustion vulnerability in the plistlib module of CPython, the reference implementation of the Python programming language maintained by the Python Software Foundation. The plistlib module is responsible for parsing plist (property list) files, commonly used for configuration and data serialization, especially on macOS and iOS platforms. The vulnerability stems from the module reading data sizes directly from the plist file without adequate validation or bounds checking. An attacker who can supply a malicious plist file can specify arbitrarily large size values, causing the parser to allocate excessive memory buffers. This uncontrolled resource consumption can lead to out-of-memory conditions, causing the Python process to crash or become unresponsive, resulting in a denial of service. The vulnerability affects multiple CPython versions, including 3.11.0 through 3.15.0a1, and even the initial version 0, indicating a long-standing issue. The CVSS 4.0 vector indicates local attack vector (AV:L), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and limited impact on availability (VA:L), with no impact on confidentiality or integrity. The vulnerability is categorized under CWE-400, highlighting uncontrolled resource consumption. No known exploits have been reported in the wild, and no official patches have been linked yet, suggesting that mitigation may rely on cautious handling of plist files or third-party patches. This vulnerability primarily impacts applications and systems that use CPython to parse plist files, especially those that process untrusted or user-supplied plist data.

CWE-400Uncontrolled Resource Consumption (opens in a new tab)
Class weaknessLikelihood of exploit: High
The product does not properly control the allocation and maintenance of a limited resource.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design
Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place.
Architecture and Design
Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or; uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed.
Architecture and Design
Ensure that protocols have specific limits of scale placed on them.
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
XML Ping of the Death (opens in a new tab)
Regular Expression Exponential Blowup (opens in a new tab)
Sustained Client Engagement (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, 18:32 UTC

WeaknessesCWE-400

Technical details

References

Community reviews

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