EUVD-2026-65481
GHSA-97g4-hhwh-c697
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
DTLS server reachable over UDP with no authentication required; impact is availability-only via memory exhaustion with no confidentiality or integrity consequence.
Primary rating from Vendor (openssl).
CVSS VectorVendor: openssl
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
6DescriptionCVE.org
Issue summary: Receiving a DTLS record for a future epoch while a handshake is in progress causes OpenSSL to buffer far more memory than the record itself requires.
Impact summary: A peer can use a small amount of network traffic to make an OpenSSL DTLS endpoint retain a disproportionately large amount of memory, which may lead to a Denial of Service.
CWE: CWE-405: Asymmetric Resource Consumption (Amplification)
Description: While a DTLS handshake is in progress, a peer may legitimately have already moved on to the next epoch (for example, having sent its ChangeCipherSpec and Finished messages) before the local endpoint has processed the same transition, typically because of reordering on the underlying UDP transport. OpenSSL buffers such early records so that they can be processed once the local endpoint catches up.
Buffering a record currently retains the entire read buffer it arrived in, which is sized to hold the largest possible DTLS record (around 16 kilobytes), rather than just the bytes that make up the record itself. Up to 100 such records may be buffered per connection. As a result, a peer that sends a stream of small forged records claiming to belong to the next epoch can cause an OpenSSL DTLS endpoint to retain around 1.7 megabytes of memory, despite sending only a small fraction of that amount of data over the network.
An attacker therefore gains a memory amplification factor of around 1200, and can multiply the effect across as many associations as it is able to open, making this a remote memory exhaustion Denial of Service risk for DTLS servers. Since the memory retained per connection remains bounded, and any limit an application already places on the number of concurrent associations also bounds the total exposure, this issue has been assessed as Low severity.
FIPS impact: no
No FIPS modules are affected by this issue as the affected code is outside the OpenSSL FIPS module boundary.
OpenSSL 4.0, 3.6, 3.5, 3.4, 3.0, 1.1.1 and 1.0.2 are vulnerable to this issue.
OpenSSL 4.0 users should upgrade to OpenSSL 4.0.2. OpenSSL 3.6 users should upgrade to OpenSSL 3.6.4. OpenSSL 3.5 users should upgrade to OpenSSL 3.5.8. OpenSSL 3.4 users should upgrade to OpenSSL 3.4.7. OpenSSL 3.0 users should upgrade to OpenSSL 3.0.22.
Premium support customers only: OpenSSL 1.1.1 users should upgrade to OpenSSL 1.1.1zi OpenSSL 1.0.2 users should upgrade to OpenSSL 1.0.2zr
This issue was reported on 18 May 2026 by Amazon Web Services. The fix has been developed by Matt Caswell.
-- cut (non-publishing metadata for internal use) -- Reported by: Amazon Web Services Fixed by: Matt Caswell
Articles & Coverage 1
AnalysisAI
DTLS memory exhaustion in OpenSSL allows unauthenticated remote peers to consume disproportionate server memory during handshake processing. Sending small forged records that claim a future epoch triggers OpenSSL to buffer the entire ~16 KB read buffer rather than just the actual record bytes, yielding an amplification factor of approximately 1,200× per record; up to 100 such records may be queued per connection, exposing roughly 1.7 MB of server memory per association from a negligible volume of transmitted data. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires that the target be running an OpenSSL DTLS server endpoint - TLS-only servers over TCP are not affected. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The official CVSS 7.5 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) accurately reflects the network-reachable, unauthenticated nature of the attack and high availability impact, yet OpenSSL itself assesses severity as Low because the per-connection memory footprint is bounded at approximately 1.7 MB and any application-level ceiling on concurrent DTLS associations directly caps total exposure. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An unauthenticated remote attacker opens a large number of concurrent DTLS handshakes with a target server and, during each handshake, transmits a stream of small forged UDP datagrams bearing records that claim to belong to the next handshake epoch. Each such record causes OpenSSL to buffer a full 16 KB read buffer; with up to 100 records buffered per connection, each association consumes approximately 1.7 MB of server memory from minimal transmitted data. … |
| Remediation | The primary remediation is to upgrade to the appropriate patched OpenSSL release: 4.0.2, 3.6.4, 3.5.8, 3.4.7, or 3.0.22 depending on the deployed branch. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all systems running OpenSSL with DTLS enabled, prioritizing production communication services. …
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Threat intelligence, references, and detailed analysis are available after sign-in.
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External POC / Exploit Code
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