ProFTPD Project up to 1.3.9 Mod Sftp fxp_packet_read packet_len heap-based overflow

Summaryinfo

A vulnerability categorized as problematic has been discovered in ProFTPD Project ProFTPD up to 1.3.9. Affected by this vulnerability is the function fxp_packet_read of the component Mod Sftp. The manipulation of the argument packet_len results in heap-based overflow. This vulnerability is cataloged as CVE-2026-53994. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in ProFTPD Project ProFTPD up to 1.3.9. It has been classified as problematic. Affected is the function fxp_packet_read of the component Mod Sftp. The manipulation of the argument packet_len with an unknown input leads to a heap-based overflow vulnerability. CWE is classifying the issue as 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(). This is going to have an impact on integrity, and availability. CVE summarizes:

ProFTPD mod_sftp contains a heap-based buffer overflow reachable by an authenticated SFTP user. The fxp_packet_read() function accepts the attacker-supplied 32-bit big-endian SFTP packet length without a minimum sanity check. A value of 0 causes an unsigned subtraction elsewhere in the read path to underflow to approximately 4 GB. That oversized request reaches the core memory allocator, where the rounded size is computed in size_t but passed to new_block() as a 32-bit int; the low 32 bits of 0x100000000 are 0, so new_block() returns a small (~512-byte) block while the caller is told it received ~4 GB. The subsequent fill loop then streams attacker-controlled bytes past the end of the 544-byte allocation, producing an attacker-controlled heap buffer overflow. An authenticated user can crash the per-connection ProFTPD session child on demand with a single malformed SFTP packet (packet_len=0 followed by a body greater than approximately 544 bytes), producing reliable authenticated remote denial of service. Depending on heap layout and adjacent allocations, heap metadata corruption and further consequences beyond denial of service may be possible, though only denial of service is demonstrated by the supplied proof of concept.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-53994 since 06/11/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. Technical details are known, but there is no available exploit.

Upgrading to version 1.3.10 eliminates this vulnerability.

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Productinfo

Type

• Project Management Software

Vendor

• ProFTPD Project

Name

• ProFTPD

Version

• 1.3.0
• 1.3.1
• 1.3.2
• 1.3.3
• 1.3.4
• 1.3.5
• 1.3.6
• 1.3.7
• 1.3.8
• 1.3.9

License

• open-source

CPE 2.3info

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CPE 2.2info

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