CVE-2026-3547Network attack vector

Remote process crash via ALPN loop-bound error

Published Mar 19, 2026 · Updated Mar 19, 2026

Out-of-bounds read in wolfSSL before 5.9.0 allows remote attackers to crash an ALPN-enabled process using a crafted protocol list. The ALPN protocol-list parsing loop compares a cumulative index that includes its starting offset against the remaining size instead of the full input length, allowing iteration beyond the buffer. Exposure requires HAVE_ALPN or --enable-alpn; ALPN is disabled by default but enabled by several compatibility configurations, and the reported consequence is a process crash.

CVSS severity7.5
High
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in wolfSSL before 5.9.0 allows remote attackers to crash an ALPN-enabled process using a crafted protocol list. The ALPN protocol-list parsing loop compares a cumulative index that includes its starting offset against the remaining size instead of the full input length, allowing iteration beyond the buffer. Exposure requires HAVE_ALPN or --enable-alpn; ALPN is disabled by default but enabled by several compatibility configurations, and the reported consequence is a process crash.

The record

CVE
CVE-2026-3547
Published
Mar 19, 2026
Updated
Mar 19, 2026
Vendor
wolfSSL
Product
wolfSSL
Classifications
CWE-125, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 19, 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 <5.9.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

wolfSSL · wolfSSLversion=0 <5.9.0

Published CVSS scores

7.5wolfSSL Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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