Mesop Class Pollution vulnerability leads to DoS and Jailbreak attacks

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2025-30358: 0.71% estimated exploitation activity in the next 30 days; percentile 53.58 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

From @jackfromeast and @superboy-zjc: We have identified a class pollution vulnerability in Mesop (<= 0.14.0) application that allows attackers to overwrite global variables and class attributes in certain Mesop modules during runtime. This vulnerability could directly lead to a denial of service (DoS) attack against the server. Additionally, it could also result in other severe consequences given the application's implementation, such as identity confusion, where an attacker could impersonate an assistant or system role within conversations. This impersonation could potentially enable jailbreak attacks when interacting with large language models (LLMs). Just like the Javascript's prototype pollution, this vulnerability could leave a way for attackers to manipulate the intended data-flow or control-flow of the application at runtime and lead to severe consequnces like RCE when gadgets are available.

Published by the source

27 Mar 2025, 18:14 UTC

Last modified by the source

7 Jul 2026, 17:56 UTC

Source last checked

26 Oct 2026, 13:31 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-f3mf-hm6v-jfhh

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-f3mf-hm6v-jfhh

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# Patch Next advisory brief: CVE-2025-30358

Advisory: Mesop Class Pollution vulnerability leads to DoS and Jailbreak attacks
IDs: CVE-2025-30358, GHSA-f3mf-hm6v-jfhh
Record: https://patchnext.com/advisories/cve-2025-30358 (revision 2, source checked 26 Oct 2026, 13:31 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: mesop 0.14.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI mesop: affected < 0.14.1; fixed in 0.14.1

## Suggested inspection (read-only)
- `python -m pip show mesop`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on mesop.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-f3mf-hm6v-jfhh (OSV record GHSA-f3mf-hm6v-jfhh lists affected ranges: PyPI mesop >=0 <0.14.1 (fixed))
- Verified: https://github.com/advisories/GHSA-f3mf-hm6v-jfhh (GitHub-reviewed advisory GHSA-f3mf-hm6v-jfhh lists affected ranges: PyPI mesop >=0 <0.14.1)

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