CVE-2026-18798Network attack vector

QUIC server crash via double-freed QRX object

Published Aug 25, 2026 · Updated Aug 25, 2026

Double free in OpenSSL 3.5.0 through 3.5.7, 3.6.0 through 3.6.3, and 4.0.0 through 4.0.1 allows remote attackers to crash QUIC servers. port_bind_channel() frees the QRX object after rejecting a short destination connection ID, and port_default_packet_handler() frees it again. A malformed INITIAL packet with a destination connection ID shorter than eight bytes reaches this path without authentication; the reported consequence is process termination, not code execution.

CVSS severityUnavailable
Unscored
EPSS probability1.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Double free in OpenSSL 3.5.0 through 3.5.7, 3.6.0 through 3.6.3, and 4.0.0 through 4.0.1 allows remote attackers to crash QUIC servers. port_bind_channel() frees the QRX object after rejecting a short destination connection ID, and port_default_packet_handler() frees it again. A malformed INITIAL packet with a destination connection ID shorter than eight bytes reaches this path without authentication; the reported consequence is process termination, not code execution.

The record

CVE
CVE-2026-18798
Published
Aug 25, 2026
Updated
Aug 25, 2026
Vendor
OpenSSL Project
Product
OpenSSL
Classifications
CWE-415, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 25, 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=3.5.0 <3.5.8
  2. Affected versionversion=3.6.0 <3.6.4
  3. Affected versionversion=4.0.0 <4.0.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenSSL Project · OpenSSLversion=3.5.0 <3.5.8; version=3.6.0 <3.6.4; version=4.0.0 <4.0.2

Published CVSS scores

No CVSS assessment is available in this record.

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-415Double Free
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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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