CVE-2026-5264Public exploitNetwork attack vector

Memory corruption via unbounded DTLS ACK records

Published Apr 9, 2026 · Updated Apr 9, 2026

Heap buffer overflow in DTLS 1.3 ACK processing in wolfSSL before 5.9.1 allows remote attackers to corrupt memory via crafted ACKs. Dtls13RtxAddAck and Dtls13WriteAckMessage track and encode an unbounded ACK-record list, and a 16-bit computed length can wrap before allocation. A DTLS 1.3 endpoint must process more than 4,096 attacker-supplied record numbers; the demonstrated case writes roughly 65 KB beyond the heap buffer, threatening integrity and service availability.

CVSS severity8.3
High
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer overflow in DTLS 1.3 ACK processing in wolfSSL before 5.9.1 allows remote attackers to corrupt memory via crafted ACKs. Dtls13RtxAddAck and Dtls13WriteAckMessage track and encode an unbounded ACK-record list, and a 16-bit computed length can wrap before allocation. A DTLS 1.3 endpoint must process more than 4,096 attacker-supplied record numbers; the demonstrated case writes roughly 65 KB beyond the heap buffer, threatening integrity and service availability.

The record

CVE
CVE-2026-5264
Published
Apr 9, 2026
Updated
Apr 9, 2026
Vendor
wolfSSL
Product
wolfSSL
Classifications
CWE-122, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <5.9.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

wolfSSL · wolfSSLversion=0 <5.9.1

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
8.3wolfSSL Inc.CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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