VulnerabilityPublished 20 Mar 2026Updated 25 Mar 2026

CVE-2026-33057: mesop · Code Injection

Affects mesopSource CVE Database V5

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Not known to be exploited · public detection template (Nuclei) · CVSS 9.8 Critical : upgrade to 1.2.3 as a priority.

Data as of 31 Oct 2026, 08:20 UTC

CVSS 3.1 base score

9.8Critical

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

EPSS: 5.2% chance of exploitation in 30 days – higher than 92% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.2.3

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
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: 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: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to 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 20 Mar 2026
Detectable: evidence found.
nuclei template: Mesop AI Sandbox <= 1.2.2 - Remote Code Execution
Weaponized: evidence found.
Public exploit code: GitHub proofs of concept
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), GitHub proofs of concept, the Metasploit, Exploit-DB and nuclei-templates index as of 30 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.
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 mesop to 1.2.3.

Affected software

Product	Affected	Fixed in
mesop-devmesop	Affected <1.2.3	Fixed in 1.2.3
PyPImesop`pkg:pypi/mesop`Other threats	Affected <1.2.3	Fixed in 1.2.3

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

AI-suggested

The primary mitigation is to upgrade all mesop instances to version 1.2.3 or later, where this vulnerability is fixed. Until upgrades can be applied, organizations should immediately restrict network access to the affected /exec-py endpoint, ideally by firewall rules or network segmentation, to prevent unauthorized HTTP requests. Disabling or removing the ai/testing module and the embedded Flask debugging server in production environments is strongly recommended to reduce attack surface. Monitoring and logging HTTP requests to detect suspicious activity targeting this endpoint can provide early warning of exploitation attempts. Additionally, running mesop with the least privilege possible and employing runtime application self-protection (RASP) or endpoint detection and response (EDR) solutions may help detect or block malicious code execution. Regular security audits and code reviews should be conducted to identify similar unsafe code execution patterns.

Description

Mesop is a Python-based UI framework that allows users to build web applications. In versions 1.2.2 and below, an explicit web endpoint inside the ai/ testing module infrastructure directly ingests untrusted Python code strings unconditionally without authentication measures, yielding standard Unrestricted Remote Code Execution. Any individual capable of routing HTTP logic to this server block will gain explicit host-machine command rights. The AI codebase package includes a lightweight debugging Flask server inside ai/sandbox/wsgi_app.py. The /exec-py route accepts base_64 encoded raw string payloads inside the code parameter natively evaluated by a basic POST web request. It saves it rapidly to the operating system logic path and injects it recursively using execute_module(module_path...). This issue has been fixed in version 1.2.3.

Impact

This vulnerability allows attackers to gain full control over affected systems running vulnerable mesop versions by executing arbitrary Python code remotely without authentication. The impact includes complete compromise of confidentiality, integrity, and availability of the host system. Attackers can steal sensitive data, modify or delete files, install malware or backdoors, pivot within internal networks, and disrupt services. Given mesop's role as a UI framework for web applications, exploitation could lead to compromise of web-facing servers, potentially exposing customer data or internal resources. The ease of exploitation and lack of required privileges or user interaction make this a highly dangerous threat. Organizations using mesop in production environments are at significant risk of targeted attacks or automated exploitation once public details become widely known.

Summary

The vulnerability CVE-2026-33057 affects the mesop Python UI framework, specifically versions 1.2.2 and earlier. Mesop includes a lightweight Flask debugging server within its AI codebase, notably in ai/sandbox/wsgi_app.py, which exposes an endpoint /exec-py. This endpoint accepts POST requests containing a base64-encoded Python code string in the 'code' parameter. The server decodes and saves this code to the operating system path, then executes it recursively using the execute_module function. Critically, this endpoint lacks any authentication or input validation, allowing any remote attacker capable of sending HTTP requests to the server to execute arbitrary Python code on the host machine. This constitutes an unrestricted remote code execution (RCE) vulnerability classified under CWE-94 (Improper Control of Generation of Code). The vulnerability has a CVSS 3.1 score of 9.8, indicating critical severity due to its network attack vector, no required privileges or user interaction, and full impact on confidentiality, integrity, and availability. The issue was publicly disclosed on March 20, 2026, and fixed in mesop version 1.2.3. No known exploits have been reported in the wild yet. The flaw stems from the design choice to include a debugging endpoint that executes arbitrary code without safeguards, posing a severe risk if exposed in production environments.

CWE-94Improper Control of Generation of Code (Code Injection) (opens in a new tab)
Base weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #10OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.
Architecture and Design · Refactoring
Refactor your program so that you do not have to dynamically generate code.
Architecture and Design
Run your code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which code can be executed by your product.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
OWASP Cheat Sheets
Server Side Request Forgery Prevention (opens in a new tab)
Unvalidated Redirects and Forwards (opens in a new tab)
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Abuse Case (opens in a new tab)
OWASP ASVS 4.0.3
V5.2.8 (opens in a new tab)
V5.2.5 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
Leverage Executable Code in Non-Executable Files (opens in a new tab)
Manipulating User-Controlled Variables (opens in a new tab)
Code Injection (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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CVE-2026-33057: mesop · Code Injection

Exploitation evidence

What to do

Affected software

Description

Impact

Summary

Nuclei detection templates

Proofs of concept on GitHub

References

Community reviews

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 27 Mar 2026, 18:53 UTC

Public exploits and detectiona Nuclei detection template, GitHub proofs of concept

WeaknessesCWE-94

Technical details

References

Community reviews

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