CyberSecBulletin
CVE-2026-63090NVD status: Analyzed

proftpd: Heap-based Buffer Overflow

Published Updated By the CyberSecBulletin desk

CVE-2026-63090 is a high-severity heap-based buffer overflow vulnerability in proftpd, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists versions 1.3.9c, 1.3.10rc3 as the first without the flaw, so updating proftpd to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.93% chance of exploitation within 30 days, higher than 61% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update proftpd to 1.3.9c or 1.3.10rc3, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
Proftpdproftpdbefore 1.3.9c; 1.3.10rc1 up to, but not including, 1.3.10rc31.3.9c, 1.3.10rc3

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (vulncheck.com).

Scoring systemScoreSeverityScored by
CVSS 4.08.7HighCNA (vulncheck.com)
CVSS 3.18.8HighCNA (vulncheck.com)

Official 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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Heap-based Buffer Overflow

The product writes past the end of a buffer that was allocated on the heap.

How developers prevent this class of flaw

  • Pre-design: Use a language or compiler that performs automatic bounds checking.
  • Use an abstraction library to abstract away risky APIs. Not a complete solution.
  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.

More Heap-based Buffer Overflow vulnerabilities (CWE-122)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other references

Other vulnerabilities in proftpd

All proftpd vulnerabilities

Recent Heap-based Buffer Overflow vulnerabilities

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