CVE-2026-33054Public exploitNetwork attack vector

Unauthenticated file overwrite and deletion via state token

Published Mar 20, 2026 · Updated Mar 20, 2026

Path traversal in Mesop before 1.2.3 allows remote attackers to overwrite or delete arbitrary files through the /ui endpoint. The ui_stream handler passes an untrusted protobuf state_token to FileStateSessionBackend._make_file_path, which joins it to base_dir without rejecting traversal segments or verifying containment. Exploitation requires the disk-based FileStateSessionBackend; targeting a non-msgpack file can also trigger repeated application crashes.

CVSS severity10.0
Critical
EPSS probability0.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Path traversal in Mesop before 1.2.3 allows remote attackers to overwrite or delete arbitrary files through the /ui endpoint. The ui_stream handler passes an untrusted protobuf state_token to FileStateSessionBackend._make_file_path, which joins it to base_dir without rejecting traversal segments or verifying containment. Exploitation requires the disk-based FileStateSessionBackend; targeting a non-msgpack file can also trigger repeated application crashes.

The record

CVE
CVE-2026-33054
Published
Mar 20, 2026
Updated
Mar 20, 2026
Vendor
mesop-dev
Product
Mesop
Classifications
CWE-22, T1485
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.2.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

mesop-dev · Mesopversion=< 1.2.3

Published CVSS scores

10.0GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
9.8NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1485Data Destruction

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo