CVE-2026-33645Network attack vector

Authenticated arbitrary file write via crafted checksum

Published Mar 26, 2026 · Updated Mar 26, 2026

Path traversal in Fireshare 1.5.1 allows remote authenticated users to write arbitrary files through its chunked upload endpoint. The /api/uploadChunked handler in app/server/fireshare/api.py inserts the attacker-controlled checkSum multipart value into os.path.join paths without normalization, sanitization, or a containment check. A valid Fireshare account and enabled upload feature are required; writes reach any filesystem location writable by the Fireshare process, enabling data corruption or local persistence.

CVSS severity7.1
High
EPSS probability0.43%
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 Fireshare 1.5.1 allows remote authenticated users to write arbitrary files through its chunked upload endpoint. The /api/uploadChunked handler in app/server/fireshare/api.py inserts the attacker-controlled checkSum multipart value into os.path.join paths without normalization, sanitization, or a containment check. A valid Fireshare account and enabled upload feature are required; writes reach any filesystem location writable by the Fireshare process, enabling data corruption or local persistence.

The record

CVE
CVE-2026-33645
Published
Mar 26, 2026
Updated
Mar 26, 2026
Vendor
Shane Israel
Product
Fireshare
Classifications
CWE-73, CWE-22, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 26, 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== 1.5.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Shane Israel · Fireshareversion== 1.5.2

Published CVSS scores

8.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
7.1GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-73External Control of File Name or Path
CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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