ProFTPD up to 1.3.9b/1.3.10rc2 Mod Sftp fxp.c pr_fsio_stat heap-based overflow

Summaryinfo

A vulnerability classified as very critical was found in ProFTPD up to 1.3.9b/1.3.10rc2. The impacted element is the function pr_fsio_stat of the file fxp.c of the component Mod Sftp. Such manipulation leads to heap-based overflow. This vulnerability is listed as CVE-2026-63090. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability was found in ProFTPD up to 1.3.9b/1.3.10rc2. It has been rated as very critical. Affected by this issue is the function pr_fsio_stat of the file fxp.c of the component Mod Sftp. The manipulation with an unknown input leads to a heap-based overflow vulnerability. Using CWE to declare the problem leads to CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). Impacted is confidentiality, integrity, and availability. CVE summarizes:

ProFTPD before 1.3.9c and 1.3.10rc3 contains a heap-based buffer overflow vulnerability in the mod_sftp module that allows authenticated low-privilege attackers to achieve arbitrary code execution by sending crafted SFTP packet fragments exceeding the 16 KB reassembly buffer in the fxp.c component. Attackers can supply oversized fragments to trigger an incorrectly conditioned reallocation, corrupt pool freelist metadata, overwrite the root_fs BSS global pointer to reference a fake filesystem struct, and redirect pr_fsio_stat() to system() via a crafted RENAME request.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-63090 since 07/15/2026. The exploitation is known to be easy. The attack may be launched remotely. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 07/20/2026).

Upgrading to version 1.3.9c or 1.3.10rc3 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-45960). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Type

• File Transfer Software

Name

• ProFTPD

Version

• 1.3.9a
• 1.3.9b
• 1.3.10rc1
• 1.3.10rc2

License

• open-source

Website

• Product: https://github.com/proftpd/proftpd/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Discussion