libxml2: Heap-based Buffer Overflow (CVE-2026-63090)

What is affected, what to do

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.

Update ProFTPD to version 1.3.9c, ProFTPD to version 1.3.10rc3.

Affected

• ProFTPD lt *..1.3.9c
• ProFTPD lt 1.3.10rc1..1.3.10rc3

Fixed in

• ProFTPD 1.3.9c
• ProFTPD 1.3.10rc3

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Metrics

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2

NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

Read in glossary

High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.

CRA

The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

Read in glossary

From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.

ISO/IEC 27001

ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

Read in glossary

Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

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: BSI WID Portal

Vendors and products

• Meinberg Lantime
• Open Source Proftpd
• ProFTPD ProFTPD

Weakness classes (CWE)

• CWE-122Heap-based Buffer Overflow

  Variant

  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().

  Entry at MITRE CWE-122

References & sources

• nlnetlabs.nldownloads/unbound/CVE-2026-56444.txtVendor advisory, Vendor advisory
• nlnetlabs.nldownloads/unbound/CVE-2026-50243.txtVendor advisory, Vendor advisory
• nlnetlabs.nldownloads/unbound/CVE-2026-40691.txtVendor advisory, Vendor advisory
• nlnetlabs.nldownloads/unbound/CVE-2026-50252.txtVendor advisory, Vendor advisory
• kb.isc.orgCVE-2026-11721Vendor advisory
• downloads.isc.orgisc/bind9/9.20.26Patch
• downloads.isc.orgisc/bind9/9.21.24Patch
• nlnetlabs.nldownloads/unbound/CVE-2026-55991.txtVendor advisory, Vendor advisory
• nlnetlabs.nldownloads/unbound/CVE-2026-40622.txteuvd, Vendor advisory
• sourceware.orgbugzilla/show_bug.cgi?id=34015
• Siemens ProductCERTproductcert/html/ssa-082556.html
• nlnetlabs.nldownloads/unbound/CVE-2026-50046.txtVendor advisory, Vendor advisory
• kb.isc.orgCVE-2026-10723Vendor advisory
• kb.isc.orgCVE-2026-13321Vendor advisory
• nlnetlabs.nldownloads/unbound/CVE-2026-55973.txtVendor advisory, Vendor advisory
• openwall.comlists/oss-security/2026/07/06/5Mailing list, Release notes
• marc.info?l=openssh-unix-dev&m=178333966933090&w=2Release notes
• openssh.orgreleasenotes.htmlRelease notes
• kb.isc.orgCVE-2026-11331Vendor advisory
• sourceware.orgbugzilla/show_bug.cgi?id=34014

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

1. 21.07.2026Record modifiedCISA ADP

   CISA assessment (SSVC): exploitation: none known, automatable: no

   Show the original change

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   SSVC assessment	added	—	{"id":"CVE-2026-63090","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-07-21T15:33:06.549976Z"}

   Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0