Excessive Memory Use Buffering DTLS Records for a Future Epoch (CVE-2026-54874)

What is affected, what to do

A flaw was found in OpenSSL. Receiving a DTLS (Datagram Transport Layer Security) record for a future epoch while a handshake is in progress causes OpenSSL to buffer an excessive amount of memory.

Update OpenSSL to version 4.0.2, OpenSSL to version 3.6.4, OpenSSL to version 3.5.8.

Affected

• OpenSSL lt 4.0.0..4.0.2
• OpenSSL lt 3.6.0..3.6.4
• OpenSSL lt 3.5.0..3.5.8
• OpenSSL lt 3.4.0..3.4.7
• OpenSSL lt 3.0.0..3.0.22
• OpenSSL lt 1.1.1..1.1.1zi
• OpenSSL lt 1.0.2..1.0.2zr

Fixed in

• OpenSSL 4.0.2
• OpenSSL 3.6.4
• OpenSSL 3.5.8
• OpenSSL 3.4.7
• OpenSSL 3.0.22
• OpenSSL 1.1.1zi
• OpenSSL 1.0.2zr

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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

A flaw was found in OpenSSL. Receiving a DTLS (Datagram Transport Layer Security) record for a future epoch while a handshake is in progress causes OpenSSL to buffer an excessive amount of memory. This allows a peer to cause memory exhaustion, eventually resulting in a denial of service, using a small amount of network traffic.

Source: redhat_csaf, Ubuntu Security Notices, suse_csaf, Debian Security Advisories, BSI WID Portal, BSI CSAF, cvelistv5, NVD (NIST), Microsoft Security Update Guide

Weakness classes (CWE)

• CWE-405Asymmetric Resource Consumption (Amplification)

  Class

  The product does not properly control situations in which an adversary can cause the product to consume or produce excessive resources without requiring the adversary to invest equivalent work or otherwise prove authorization, i.e., the adversary's influence is "asymmetric."

  Entry at MITRE CWE-405

References & sources

• openssl-library.orgOpenSSL AdvisoryVendor advisory
• github.com4.0.2 git commitPatch
• github.com3.6.4 git commitPatch
• github.com3.5.8 git commitPatch
• github.com3.4.7 git commitPatch
• github.com3.0.22 git commitPatch

Reanalysis & status changes

Chronological NVD audit events for this CVE — reanalyses, CVSS updates, CPE diffs.

1. Initial Analysis11.09.2026nvd@nist.gov

   • CPE Configuration: after OR *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.5.0 up to (excluding) 3.5.8 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.6.0 up to (excluding) 3.6.4 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 4.0.0 up to (excluding) 4.0.2 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.4.0 up to (excluding) 3.4.7 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 1.0.2 up to (excluding) 1.0.2zr *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 1.1.1 up to (excluding) 1.1.1zi *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.0.0 up to (excluding) 3.0.22
   • Reference Type: after OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/4808b5d64176451f3d93d87d0ac9c81a9b13fb23 Types: Patch
   • Reference Type: after OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/7110cb2f75806d0bf809eb2f90790d477900be40 Types: Patch
   • Reference Type: after OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/a0c8ec557d9cac078f032d76cdf684fe743eb382 Types: Patch

2. CVE Modified25.08.2026134c704f-9b21-4f2e-91b3-4a467353bcc0

   • CVSS V3.1: after AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
   • SSVC: after {"id":"CVE-2026-54874","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technical…

3. New CVE Received25.08.2026openssl-security@openssl.org

   • Affected: after OpenSSL
   • Description: after 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
   • CWE: after CWE-405
   • Reference: after https://github.com/openssl/openssl/commit/4808b5d64176451f3d93d87d0ac9c81a9b13fb23