FreeBSD: Out-of-bounds Read (CVE-2026-84782)

What is affected, what to do

A flaw was found in OpenSSL. The Datagram Transport Layer Security (DTLS) retransmission mechanism fails to properly handle handshake message writes that are suspended before completion.

Update OpenSSL to version 4.0.3, OpenSSL to version 3.6.5, OpenSSL to version 3.5.9.

Affected

• OpenSSL lt 4.0.0..4.0.3
• OpenSSL lt 3.6.0..3.6.5
• OpenSSL lt 3.5.0..3.5.9
• OpenSSL lt 3.4.0..3.4.8
• OpenSSL lt 3.0.0..3.0.23
• OpenSSL lt 1.1.1..1.1.1zj
• OpenSSL lt 1.0.2..1.0.2zs

Fixed in

• OpenSSL 4.0.3
• OpenSSL 3.6.5
• OpenSSL 3.5.9
• OpenSSL 3.4.8
• OpenSSL 3.0.23
• OpenSSL 1.1.1zj
• OpenSSL 1.0.2zs

Not sure whether and how you are affected? Ask a question about this vulnerability

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

A flaw was found in OpenSSL. The Datagram Transport Layer Security (DTLS) retransmission mechanism fails to properly handle handshake message writes that are suspended before completion. A remote attacker could exploit this vulnerability during handshake message retransmission, causing OpenSSL to read past the message buffer or overwrite internal state required to resume writing. This issue can result in information disclosure through out-of-bounds memory reads or cause a Denial of Service (DoS) by crashing the process.

Source: BSI WID Portal

Vendors and products

• Debian Openssl
• Freebsd Project Freebsd OS
• Open Source Openssl
• OpenSSL OpenSSL

Weakness classes (CWE)

• CWE-125Out-of-bounds Read

  Base

  The product reads data past the end, or before the beginning, of the intended buffer.

  Entry at MITRE CWE-125

References & sources

• openssl-library.orgOpenSSL AdvisoryVendor advisory
• github.com4.0.3 git commitPatch
• github.com3.6.5 git commitPatch
• github.com3.5.9 git commitPatch
• github.com3.4.8 git commitPatch
• security.freebsd.orgadvisories/FreeBSD-SA-26:69.udp.ascVendor advisory, Patch, Vendor advisory
• security.freebsd.orgadvisories/FreeBSD-SA-26:66.jail.ascVendor advisory, Patch, Vendor advisory
• security.freebsd.orgadvisories/FreeBSD-SA-26:65.kqueue.ascVendor advisory, Vendor advisory
• security.freebsd.orgadvisories/FreeBSD-SA-26:67.ktls.ascVendor advisory, Mitigation, Patch, Vendor advisory
• security.freebsd.orgadvisories/FreeBSD-SA-26:64.sysvsem.ascVendor advisory, Vendor advisory
• github.com4.0.3 git commitPatch

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. 08.10.2026Initial analysis by NVDNVD

   Newly listed as affected:

   • OpenSSL (3.4.0 – before 3.4.8; 3.5.0 – before 3.5.9; 3.6.0 – before 3.6.5; 4.0.0 – before 4.0.3; 1.0.2 – before 1.0.2zs; 1.1.1 – before 1.1.1zj; 3.0.0 – before 3.0.23)

   New references:

   • https://github.com/openssl/openssl/commit/906cf0ef1c85ca40ce69163e9086d6d3fe292943
   • https://github.com/openssl/openssl/commit/9f6b34422af7eb5dac61322e33dac1ae989fa628
   • https://github.com/openssl/openssl/commit/a383dafdd754eb5b22bf45e37e1bff9d07277a58
   • https://github.com/openssl/openssl/commit/d951e02ede8f6a6ff8150546db44b34f0518192c

   and 1 more reference

   Show 6 original changes

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   Product configuration	added	—	OR *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.4.0 up to (excluding) 3.4.8 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.5.0 up to (excluding) 3.5.9 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.6.0 up to (excluding) 3.6.5 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 4.0.0 up to (excluding) 4.0.3 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 1.0.2 up to (excluding) 1.0.2zs *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 1.1.1 up to (excluding) 1.1.1zj *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.0.0 up to (excluding) 3.0.23
   Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/906cf0ef1c85ca40ce69163e9086d6d3fe292943 Types: Patch
   Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/9f6b34422af7eb5dac61322e33dac1ae989fa628 Types: Patch
   Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/a383dafdd754eb5b22bf45e37e1bff9d07277a58 Types: Patch
   Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/d951e02ede8f6a6ff8150546db44b34f0518192c Types: Patch
   Reference type	added	—	OpenSSL Software Foundation: https://openssl-library.org/news/secadv/20260929.txt Types: Vendor Advisory

   Source identifier: nvd@nist.gov

2. 29.09.2026Record modifiedCISA ADP

   CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H

   CISA assessment (SSVC): exploitation: none known, automatable: yes

   Show 2 original changes

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   CVSS	added	—	AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
   SSVC assessment	added	—	{"id":"CVE-2026-84782","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-09-29T16:45:35.833483Z"}

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

3. 29.09.2026Receivedopenssl.org

   Weakness type: CWE-125

   Description added or changed

   New references:

   • https://github.com/openssl/openssl/commit/906cf0ef1c85ca40ce69163e9086d6d3fe292943
   • https://github.com/openssl/openssl/commit/9f6b34422af7eb5dac61322e33dac1ae989fa628
   • https://github.com/openssl/openssl/commit/a383dafdd754eb5b22bf45e37e1bff9d07277a58
   • https://github.com/openssl/openssl/commit/d951e02ede8f6a6ff8150546db44b34f0518192c

   and 1 more reference

   Show 8 original changes

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   Description	added	—	Issue summary: The DTLS retransmission logic does not correctly handle a handshake message write that is suspended part-way through. The retransmitted message can be read past the message buffer and the retransmission overwrites the internal state the suspended write needs to resume correctly. Impact summary: The retransmitted message can disclose a heap memory to the peer as plaintext handshake data or cause a crash and a Denial of Service when the read reaches an unmapped memory region. CWE: CWE-125: Out-of-bounds Read Description: DTLS handshake messages can be written out in multiple fragments, and a write can suspend mid-message (returning WANT_WRITE) if the underlying transport temporarily cannot accept more data. While such a write is suspended, the DTLS retransmission timer may independently fire and ask the retransmission logic to resend an earlier, already-acknowledged-as-sent message from its retransmit queue. The retransmission logic reused the same internal buffer and position tracking as the message that was still being written, without resetting the position back to the start of the message being retransmitted. As a result the retransmission was read starting from wherever the suspended write had left off, producing a mislabelled message whose body was leftover bytes from the other, larger message still in flight - content that was never meant to be sent at that point, and which could run past the end of the allocated buffer. Separately, even when the retransmission is positioned correctly, allowing it to run to completion while another write is suspended overwrites the same shared bookkeeping that the suspended write depends on to resume. When the application later resumes the suspended write (via a subsequent SSL_read(), SSL_write(), SSL_accept(), or SSL_connect() call), it finds that bookkeeping in a state inconsistent with the message and aborts the process in a debugging build. The fix resets the retransmission's read position to the start of the message before resending, and skips retransmission entirely whenever a handshake write is still suspended, deferring to the next call that resumes it instead. FIPS impact: no The affected code is outside the FIPS module boundary.
   Weakness type (CWE)	added	—	CWE-125
   Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/84xxx/CVE-2026-84782.json">CVE-2026-84782</a>
   Reference	added	—	https://github.com/openssl/openssl/commit/906cf0ef1c85ca40ce69163e9086d6d3fe292943
   Reference	added	—	https://github.com/openssl/openssl/commit/9f6b34422af7eb5dac61322e33dac1ae989fa628
   Reference	added	—	https://github.com/openssl/openssl/commit/a383dafdd754eb5b22bf45e37e1bff9d07277a58
   Reference	added	—	https://github.com/openssl/openssl/commit/d951e02ede8f6a6ff8150546db44b34f0518192c
   Reference	added	—	https://openssl-library.org/news/secadv/20260929.txt

   Source identifier: openssl-security@openssl.org