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OpenSSL CVE-2026-84782

| EUVDEUVD-2026-89013 HIGH
Out-of-bounds Read (CWE-125)
2026-09-29 GHSA-6w84-hw79-7wgf
Buffer Overflow Information Disclosure OpenSSL
8.2
CVSS 3.1 · Vendor
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Reach DTLS-enabled endpoint over network
  2. Exploit
    Send crafted handshake and induce retransmission
  3. Execution
    Trigger stale-offset out-of-bounds read
  4. Impact
    Crash service or leak adjacent memory

Vulnerability Assessment

Weakness
CWE
CWE-125
ASVS 5.0
V15 - Secure Coding and Architecture Bounds checking, read limits
MITRE ATT&CK

1 technique across 1 tactic: Collection

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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Exploitation Conditions

Exploitation requires the target application to use DTLS (datagram TLS, typically over UDP - e.g., VPNs, WebRTC/SRTP-DTLS, CoAP/IoT stacks) built against a vulnerable OpenSSL version (1.0.2 before zs, 1.1.1 before zj, 3.0.0 before 3.0.23, 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). The bug is reached through retransmission of DTLS handshake messages from a stale buffer offset, so the attacker must engage the DTLS handshake and cause a retransmission condition. No authentication or user interaction is required (PR:N/UI:N), but pure TLS-over-TCP deployments - the majority of OpenSSL usage - are NOT affected, which is the key factor limiting real-world exposure.
Impact

This is a genuinely elevated but not top-tier priority. The vendor CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H, base 8.2) describes a remotely reachable, unauthenticated out-of-bounds read (CWE-125) in DTLS handshake retransmission, driven primarily by A:H (availability/DoS) with only a low confidentiality leak (C:L) and no integrity impact. The single most important limiter is that this affects ONLY applications and appliances that use DTLS (datagram TLS over UDP) - the vast majority of OpenSSL deployments use TLS over TCP and are unaffected, so the ubiquitous OpenSSL footprint substantially overstates the real exposed population. No EPSS score, no CISA KEV listing, and no public exploit code are present in the input, so there is no signal of active or imminent exploitation - the risk is driven by the ubiquity of the library and the network/unauthenticated vector, not by demonstrated exploitation. Note a modest tension worth verifying: reliably reaching the stale-buffer-offset retransmission path may require inducing DTLS handshake retransmission (packet loss/reordering), which is easy for an on-path attacker but arguably nudges attack complexity above AC:L for a purely blind remote attacker.
Exploit ScenarioDerived

An attacker who can send DTLS handshake traffic to a vulnerable server or client (e.g., a DTLS-based VPN, WebRTC, or IoT/CoAP endpoint) crafts conditions that force retransmission of handshake messages, causing the stack to read from a stale buffer offset. The resulting out-of-bounds read crashes the process or service (denial of service) and may leak a small amount of adjacent memory. No public exploit code is identified at time of analysis; exploitation is remote and unauthenticated but constrained to DTLS-enabled deployments.
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
1 public PoC Patch available 0.4% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 29, 2026

Out-of-bounds read in OpenSSL's DTLS handshake retransmission path allows a remote, unauthenticated attacker to trigger a memory read past a stale buffer offset, crashing the DTLS endpoint (availability impact rated High) and potentially exposing a limited amount of adjacent process memory (confidentiality impact rated Low). Affected deployments are those built against OpenSSL 1.0.2 before 1.0.2zs, 1.1.1 before 1.1.1zj, 3.0.0 before 3.0.23, 3.4.0 before 3.4.8, 3.5.0 before 3.5.9, 3.6.0 before 3.6.5, or 4.0.0 before 4.0.3 that actually terminate DTLS-over-UDP sessions such as VPN concentrators, WebRTC/SRTP endpoints, and CoAP/IoT stacks; pure TLS-over-TCP deployments, the dominant use of OpenSSL, are not exposed. No public exploit code has been identified at time of analysis and the issue is not confirmed as actively exploited (not in CISA KEV); the CVSS 8.2 score reflects the unauthenticated network reachability of the DTLS handshake rather than broad applicability, so real-world priority is elevated but capped by the narrow DTLS-only attack surface.

RemediationAI

Vendor-released patches are available: upgrade to OpenSSL 4.0.3 (or the corresponding fixed branch releases 3.6.5, 3.5.9, 3.4.8, 3.0.23, 1.1.1zj, and 1.0.2zs), which are the versions that close the stale buffer offset issue along with the other CVEs batched into the same security release - see the release notes at https://github.com/openssl/openssl/releases/tag/openssl-4.0.3 and the advisory at https://openssl-library.org/news/secadv/20260929.txt, and note that the upstream commits listed in the NVD record should be backported if you maintain a vendored or heavily patched tree. Because the defect is confined to the DTLS handshake retransmission path, the most effective compensating control for organizations that cannot patch promptly is to disable DTLS entirely on exposed listeners and require TLS over TCP; the trade-off is loss of UDP-friendly transport semantics (higher latency on lossy links, no NAT rebinding support, and no SRTP/WebRTC media path), so voice/video and constrained IoT endpoints may need a different transport or an interim edge proxy. If DTLS must remain enabled, terminate it at a hardened front end (load balancer or DTLS proxy) that can be updated independently of the backend, drop unsolicited inbound DTLS from untrusted networks, rate-limit handshake initiations, and enable process-level crash supervision/restart so that an induced abort degrades availability as little as possible; be aware that rate limiting and restarts mitigate the availability impact but do not eliminate the out-of-bounds read or the small potential memory leak, and that no public exploit code was identified at time of analysis - so these measures are precautionary rather than responses to observed attack traffic. After patching, verify the running version with openssl version -a and confirm no application bundles a stale statically linked libssl.

Affected VersionsENISA

OpenSSL 3.5.0 <3.5.9
OpenSSL 3.6.0 <3.6.5
OpenSSL 3.4.0 <3.4.8
OpenSSL 4.0.0 <4.0.3
OpenSSL 3.0.0 <3.0.23
OpenSSL 1.0.2 <1.0.2zs
OpenSSL 1.1.1 <1.1.1zj

Affected Packages

euvd openssl fix: 1.0.2zs, 1.1.1zj, 3.0.23, 3.4.8, 3.5.9, 3.6.5, 4.0.3

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

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Technical ContextAI · show details

DTLS is the datagram (UDP) variant of TLS, and because UDP is lossy it maintains a retransmission buffer so handshake flights can be replayed when a peer does not respond; OpenSSL tracks that buffer with a cursor/offset that should be advanced or reset as each flight is acknowledged. CVE-2026-84782 is a CWE-125 out-of-bounds read caused by retransmitting handshake messages from a stale buffer offset - the offset is not correctly synchronized with the buffer's current extent, so a retransmission reads beyond the valid region of the buffer. The vulnerability class is a memory-safety read (not a write), which is why the assessed impact vector is C:L/I:N/A:H: the primary observable outcome is a process abort from an invalid read, with a secondary possibility of leaking a small amount of heap memory into the DTLS record stream. The trigger is reachable during the handshake itself with no credentials or user interaction (PR:N/UI:N, AV:N/AC:L), but requires an application that builds against a vulnerable OpenSSL release and actively serves DTLS over UDP - e.g., OpenVPN-style tunnels, DTLS-SRTP media channels, CoAP/EDHOC IoT stacks, and any server calling DTLSv1_listen or the DTLS server/client methods. Upstream commits referenced in the NVD record (906cf0ef, 9f6b3442, a383dafd, d951e02e) are the source-level fixes for this and the other issues batched into the OpenSSL 4.0.3 security release, and the vendor advisory at openssl-library.org covers the full set of CVEs shipped together (including CVE-2026-84783, CVE-2026-35189, CVE-2026-84784, and several QUIC and side-channel fixes) - this CVE is the one highlighted as the DTLS handshake-buffer issue.

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Severity by source

Vendor (CNA) PRIMARY 8.2 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
vuln.today AI 8.2 HIGH

Remote unauthenticated DTLS handshake path (AV:N/PR:N/UI:N); out-of-bounds read yields process crash (A:H) with minor memory leak (C:L) and no integrity impact.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE 7.4 HIGH
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H
Red Hat 7.4 HIGH

Primary rating from Vendor (CNA).

CVSS VectorVendor

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
High

Lifecycle Timeline

3
CVSS changed
Sep 29, 2026 - 17:22 NVD
8.2 (HIGH)
CVE Published
Sep 29, 2026 - 13:53 github-releases
UNKNOWN (no severity yet)
CVE Published
Sep 29, 2026 - 13:53 github-releases
HIGH 8.2

Description PRE-NVD

Disclosed via GitHub release of openssl/openssl. NVD scoring and full description are pending.

Articles & Coverage 2

News 4 New OpenSSL Vulnerabilities - 4 High Severity, No POC Available Sep 30, 2026 News 4 New OpenSSL Vulnerabilities - 4 High Severity, No POC Available Sep 29, 2026

Latest POC

1 public PoC link from github

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Executive ViewAI

Why It Matters

A memory-safety flaw in OpenSSL's DTLS handshake handling can crash any internet-facing service that terminates DTLS-over-UDP sessions, including VPN concentrators, WebRTC/SRTP media gateways, and CoAP-based IoT platforms built on the impacted releases. Because the vulnerable code path is only reachable on UDP-based DTLS endpoints, the majority of the organization's TLS-over-TCP estate is unaffected, and exposure is concentrated in remote-access and real-time communications infrastructure where an outage directly disrupts workforce connectivity and customer-facing services. Leadership should treat this as a targeted availability risk to a small but business-critical set of systems rather than an enterprise-wide encryption emergency.

Business Impact: High
Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

EPSS Score
0.4%
Top 69% exploitable
Prevalence
Ubiquitous
OpenSSL underpins TLS/crypto across most Linux and networked software
Threat Intel
1
1 sources
Data Quality
8 sources
Confidence: High
EUVD 🇯🇵JVN NVD CVE.org EPSS Vulnrichment NEWS MSRC Vendor GitHub VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC Yes
EPSS 0.4%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
Yes
Human Impact
High
Technical Impact
Partial

Priority Score

61
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +41
PoC: +20
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Buffer Overflow HIGH

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
Container bci/bci-sle15-kernel-module-devel:15.7-61.25 Container bci/openjdk-devel:17.0.20.1-21.71 Container bci/openjdk-devel:21.0.12.1-25.71 Container bci/openjdk-devel:25.0.4.1-9.72 Container bci/openjdk:17.0.20.1-20.61 Container bci/openjdk:21.0.12.1-24.60 Container bci/openjdk:25.0.4.1-9.60 Container bci/python:3.13.15-88.58 Container bci/python:3.6.15-84.56 Container suse/sle15:15.7-5.23.43 Affected
Container private-registry/1.2/harbor-core:1.2.1-1.115 Container private-registry/1.2/harbor-exporter:1.2.1-1.115 Container private-registry/1.2/harbor-jobservice:1.2.1-1.113 Container private-registry/1.2/harbor-registry:1.2.1-1.115 Container private-registry/1.2/harbor-registryctl:1.2.1-1.115 Container private-registry/1.2/harbor-trivy-adapter:1.2.1-1.124 Container private-registry/harbor-core:latest Container private-registry/harbor-exporter:latest Container private-registry/harbor-jobservice:latest Container private-registry/harbor-registry:2.8.3-1.85 Container private-registry/harbor-registryctl:latest Container private-registry/harbor-trivy-adapter:0.35.1-1.87 Container suse/hpc/warewulf4-x86_64/sle-hpc-node:15.7.20.8.177 Container suse/kiosk/tigervnc-x11vnc:1.14-63.43 Container suse/mariadb:11.8.8-79.42 Image SLES15-SP7-Azure-Basic Image pr_15_7_1_0 Affected
Container private-registry/1.2/harbor-portal:1.2.1-1.124 Container private-registry/harbor-portal:latest Container suse/kea:2.6-80.9 Container suse/kiosk/firefox-esr:153.3-75.45 Container suse/kiosk/pulseaudio:17.0-73.42 Container suse/kiosk/xorg-client:21-81.7 Container suse/kiosk/xorg:21.1-83.42 Container suse/mariadb-client:11.8.8-72.32 Container suse/postgres:16.15-93.41 Container suse/postgres:16.15-contrib-93.41 Container suse/postgres:17.11-83.40 Container suse/postgres:17.11-contrib-83.40 Container suse/postgres:18.6-73.40 Container suse/rmt-server:3.1-72.2 Container suse/samba-client:4.21-75.34 Container suse/samba-server:4.21-76.36 Container suse/samba-toolbox:4.21-76.34 Container third-party/amd/amdgpu-driver:sles-15.7-30.20.1 Container third-party/amd/amdgpu-driver:sles-15.7-30.30.4 Container third-party/amd/amdgpu-driver:sles-15.7-31.10 Container third-party/amd/amdgpu-driver:sles-15.7-31.20 Container third-party/amd/amdgpu-driver:sles-15.7-31.30 Container third-party/amd/amdgpu-driver:sles-15.7-31.40.1 Container third-party/amd/amdgpu-driver:sles-15.7-31.50 Container third-party/nvidia/driver:550-sles15.7 Container third-party/nvidia/driver:570-sles15.7 Container third-party/nvidia/driver:575-sles15.7 Container third-party/nvidia/driver:580-sles15.7 Container third-party/nvidia/driver:590-sles15.7 Container third-party/nvidia/driver:595-sles15.7 Container third-party/nvidia/driver:610-sles15.7 Container third-party/nvidia/driver:615-sles15.7 Affected
Container suse/ltss/sle15.5/sle15:15.5-8.73 Affected
Container suse/ltss/sle15.6/bci-base-fips:15.6-35.106 Affected

References

Advisories & patches
ADVISORY https://access.redhat.com/errata/RHSA-2026:55543 ADVISORY https://access.redhat.com/errata/RHSA-2026:62562 ADVISORY https://access.redhat.com/errata/RHSA-2026:62790 ADVISORY https://access.redhat.com/errata/RHSA-2026:67551 ADVISORY https://access.redhat.com/errata/RHSA-2026:73496 ADVISORY https://access.redhat.com/errata/RHSA-2026:74162 ADVISORY https://access.redhat.com/errata/RHSA-2026:74166 ADVISORY https://github.com/openssl/openssl/releases/tag/openssl-4.0.3 ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-84782 ADVISORY https://seclists.org/oss-sec/2026/q3/1001 ADVISORY https://ubuntu.com/security/notices/USN-8847-1 ADVISORY https://vuldb.com/vuln/411442 ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:4412/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:4413/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:4414/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:4418/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:4419/ REF https://github.com/openssl/openssl/commit/906cf0ef1c85ca40ce69163e9086d6d3fe292943 REF https://github.com/openssl/openssl/commit/9f6b34422af7eb5dac61322e33dac1ae989fa628 REF https://github.com/openssl/openssl/commit/a383dafdd754eb5b22bf45e37e1bff9d07277a58 REF https://github.com/openssl/openssl/commit/d951e02ede8f6a6ff8150546db44b34f0518192c REF https://openssl-library.org/news/secadv/20260929.txt

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