CVE-2026-18798: Issue summary: QUIC server may double free QRX (QUIC record layer RX) object when channel creation fails for i

Q: How do I fix CVE-2026-18798?

openssl: upgrade to 3.5.8, 3.6.4, 4.0.2. Exact commands for each OS are on this page.

Q: Is CVE-2026-18798 being exploited?

CVE-2026-18798 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-18798 affect?

CVE-2026-18798 affects openssl. Severity is high (CVSS 7.5). Issue summary: QUIC server may double free QRX (QUIC record layer RX) object when channel creation fails for initial packet. Impact summary: Double free leads to heap corruption, which typically results in termination of QUIC server proce

Q: How urgent is CVE-2026-18798?

Priority 56/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

This month

HIGH 7.5REMOTEWATCHLISTUPGRADE

CVE-2026-18798 is a high-severity flaw (CVSS 7.5) affecting openssl. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Issue summary: QUIC server may double free QRX (QUIC record layer RX) object when channel creation fails for initial packet. Impact summary: Double free leads to heap corruption, which typically results in termination of QUIC server process, leading to Denial of Service. There is so far no evidence that this double free is exploitable for remote code execution, thus it is considered highly improbable. CWE: CWE-415: Double Free Description: In

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.7% (top 23%)
CISA exploited list	No
Weakness	CWE-415
Published	2026-08-25
Last modified	2026-09-23

Publisher (CNA): OpenSSL Software Foundation · Vendor: openssl

Last updated 2026-09-23 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-25 13:17 UTCPublished CVE record published
2026-09-23 16:07 UTCUpdated Record last modified

openssl openssl UPGRADE

Affected: >= 3.5.0 and < 3.5.8 · >= 3.6.0 and < 3.6.4 · >= 4.0.0 and < 4.0.2

Fixed in: 3.5.8, 3.6.4, 4.0.2

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy openssl || rpm -q openssl || openssl --version

2. UPGRADE to 3.5.8 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade openssl

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade openssl

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Exact fixes by distribution

Fedora 46 · gcl · FIXED · 2.7.1-12.fc46 · FEDORA-2026-ff383a759b · source

sudo dnf upgrade --advisory=FEDORA-2026-ff383a759b

Fedora ELN · mozjs140 · FIXED · 140.13.0-5.eln159 · FEDORA-2026-f7ed0026e0 · source

sudo dnf upgrade --advisory=FEDORA-2026-f7ed0026e0

Debian 12 · openssl · NOT AFFECTED

Debian 13 · openssl · FIXED · 3.5.7-1~deb13u2

sudo apt update && sudo apt install --only-upgrade openssl dpkg --compare-versions "$(dpkg-query -W -f='${Version}' openssl)" ge "3.5.7-1~deb13u2" && echo PATCHED || echo STILL-VULNERABLE

RHEL 10 · openssl · FIXED · openssl-3.5.8-1.el10_2

sudo dnf upgrade --advisory=RHSA-2026:67154 rpm -q openssl

RHEL 9 · openssl · FIXED · openssl-3.5.8-1.el9_8

sudo dnf upgrade --advisory=RHSA-2026:67165 rpm -q openssl

RHEL 10 · edk2 · NOT AFFECTED

RHEL 10 · shim · NOT AFFECTED

RHEL 10 · shim-unsigned-aarch64 · NOT AFFECTED

Alpine 3.22 · openssl · FIXED · openssl-3.5.8-r0

apk add --upgrade openssl apk info -v openssl

Alpine 3.23 · openssl · FIXED · openssl-3.5.8-r0

apk add --upgrade openssl apk info -v openssl

Alpine 3.24 · openssl · FIXED · openssl-3.5.8-r0

apk add --upgrade openssl apk info -v openssl

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2026-2136 · source

sudo dnf update --advisory=ALAS2023-2026-2136

Advisories and coverage

Official advisories

OpenSSL Vulnerabilities: OpenSSL 4.0.2 2026-08-25
OpenSSL Vulnerabilities: OpenSSL 3.6.4 2026-08-25

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-18798?

openssl: upgrade to 3.5.8, 3.6.4, 4.0.2. Exact commands for each OS are on this page.

Is CVE-2026-18798 being exploited?

CVE-2026-18798 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-18798 affect?

CVE-2026-18798 affects openssl. Severity is high (CVSS 7.5). Issue summary: QUIC server may double free QRX (QUIC record layer RX) object when channel creation fails for initial packet. Impact summary: Double free leads to heap corruption, which typically results in termination of QUIC server proce

How urgent is CVE-2026-18798?

Priority 56/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

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References

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