CVE-2026-53994Network attack vector

Authenticated session crash via SFTP length underflow

Published Jul 18, 2026 · Updated Jul 18, 2026

Heap-based buffer overflow in ProFTPD before 1.3.10 allows remote authenticated users to crash an SFTP session with a malformed packet. fxp_packet_read() accepts a zero 32-bit packet length, causing unsigned underflow and size truncation that allocate about 512 bytes while the fill loop treats the buffer as about 4 GB. Exploitation requires valid SFTP credentials and mod_sftp; the demonstrated result is a crash of the per-connection session child.

CVSS severity7.7
High
EPSS probability0.42%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in ProFTPD before 1.3.10 allows remote authenticated users to crash an SFTP session with a malformed packet. fxp_packet_read() accepts a zero 32-bit packet length, causing unsigned underflow and size truncation that allocate about 512 bytes while the fill loop treats the buffer as about 4 GB. Exploitation requires valid SFTP credentials and mod_sftp; the demonstrated result is a crash of the per-connection session child.

The record

CVE
CVE-2026-53994
Published
Jul 18, 2026
Updated
Jul 18, 2026
Vendor
ProFTPD Project
Product
ProFTPD
Classifications
CWE-122, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=0 <1.3.10

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

ProFTPD Project · ProFTPDversion=0 <1.3.10

Published CVSS scores

7.7VulnCheckCVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
7.5VulnCheckCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/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.

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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-122Heap-based Buffer Overflow
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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