What’s Vulnerable › Vulnerabilities

CVE-2026-63090: ProFTPD mod_sftp Heap Buffer Overflow via SFTP Packet Reassembly

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-20 · updated 2026-07-30
• Weakness: CWE-122

Description

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.

Affected products

• ProFTPD: before 1.3.9c; 1.3.10-rc1, 1.3.10-rc2 — fixed in 1.3.9c

How to fix

Upgrade to a fixed version: ProFTPD 1.3.9c. Check the vendor advisory for mitigations.

References

• https://github.com/proftpd/proftpd/blob/master/RELEASE_NOTES
• https://github.com/proftpd/proftpd/commit/4ee8701bcf425f11b3b2116e634ff3e655d918b1
• https://github.com/proftpd/proftpd/issues/2190
• https://github.com/proftpd/proftpd/releases/tag/v1.3.10rc3-3
• https://github.com/proftpd/proftpd/releases/tag/v1.3.9c
• https://www.vulncheck.com/advisories/proftpd-mod-sftp-heap-buffer-overflow-via-sftp-packet-reassembly

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