CVE-2026-18798

openssl: Issue summary: QUIC server may double free QRX (QUIC record layer RX) object when channel creation fails for initial...

CVE-2026-18798 is fixed in 14 products on 1 platform, first by libssl3t64 3.5.5-1ubuntu3.4, released August 24, 2026. It is not reported as exploited. Patch Radar priority: High.

High
CVSS
7.5
high
Exploitation
None reported
No vendor assessment
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.0170
77th percentile

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 order to validate initial packet, OpenSSL QUIC stack default packet handler (port_default_packet_handler()) creates a so-called QRX object. If the initial packet validates successfully with QRX object, the default packet handler proceeds to channel (connection object) creation. The QRX object used for packet validation is passed to port_bind_channel(), so it becomes part of the newly created connection. If port_bind_channel() fails, then it also frees the QRX object. Once port_bind_channel() returns, the port_default_packet_handler() detects the failure and proceeds to the error branch, where the same QRX object is freed for the second time. The failure in port_bind_channel() function can be induced with a relatively low effort by a malformed (non RFC 9000 compliant) INITIAL packet. If the packet carries DCID (destination connection ID) which is shorter than 8 bytes, then port_bind_channel() jumps to the error path after ossl_quic_lcidm_enrol_odcid() detects that the DCID has invalid length. FIPS impact: no The FIPS module is not affected, as the QUIC implementation is outside of the OpenSSL FIPS module boundary.

Where it's fixed

ProductFixed inFixReleased
Linux
libssl3t64 · Ubuntu 26.04.1 LTS (resolute) 3.5.5-1ubuntu3.4 libssl3t64 3.5.5-1ubuntu3.4 Aug 24, 2026
openssl · Debian 13.5 (trixie) 3.5.7-1~deb13u2 DEBIAN-CVE-2026-18798 Aug 26, 2026
openssl · Debian 14 3.6.4-1 DEBIAN-CVE-2026-18798 Aug 26, 2026
openssl · RHEL 10 3.5.8-1.el10_2 RHSA-2026:67154 Sep 14, 2026
openssl · RHEL 9 1:3.5.8-1.el9_8 RHSA-2026:67165 Sep 19, 2026
openssl · Ubuntu 26.04.1 LTS (resolute) 3.5.5-1ubuntu3.4 openssl 3.5.5-1ubuntu3.4 Aug 24, 2026
openssl · almalinux 10 1:3.5.8-1.el10_2.alma.1 ALSA-2026:67154 Sep 14, 2026
openssl · almalinux 9 1:3.5.8-1.el9_8 ALSA-2026:67165 Sep 14, 2026
openssl · amzn 2023 1:3.5.8-1.amzn2023.0.1 ALAS2023-2026-2136 Sep 14, 2026
openssl · ol 10 1:3.5.8-1.0.1.el10_2 ELSA-2026-67154-0 Sep 14, 2026
openssl · ol 9 1:3.5.8-1.0.1.el9_8 ELSA-2026-67165-0 Sep 14, 2026
openssl · rocky 10 1:3.5.8-1.el10_2 RLSA-2026:67154 Sep 15, 2026
openssl · rocky 9 1:3.5.8-1.el9_8 RLSA-2026:67165 Sep 15, 2026
openssl-3 · opensuse-leap 16.0 3.5.0-160000.10.1 OPENSUSE-SU-2026:21744-1 Sep 2, 2026
openssl-3 · sles 15.7 3.5.0-150700.5.50.1 SUSE-SU-2026:4039-1 Sep 7, 2026
openssl-3 · sles 16.0 3.5.0-160000.10.1 SUSE-SU-2026:23609-1 Sep 2, 2026
openssl-debuginfo · amzn 2023 1:3.5.8-1.amzn2023.0.1 ALAS2023-2026-2136 Sep 14, 2026
openssl-debugsource · amzn 2023 1:3.5.8-1.amzn2023.0.1 ALAS2023-2026-2136 Sep 14, 2026
openssl-devel · RHEL 9 1:3.5.8-1.el9_8 RHSA-2026:67165 Sep 19, 2026
openssl-devel · almalinux 10 1:3.5.8-1.el10_2.alma.1 ALSA-2026:67154 Sep 14, 2026
openssl-devel · almalinux 9 1:3.5.8-1.el9_8 ALSA-2026:67165 Sep 14, 2026
openssl-devel · amzn 2023 1:3.5.8-1.amzn2023.0.1 ALAS2023-2026-2136 Sep 14, 2026
openssl-devel · ol 10 1:3.5.8-1.0.1.el10_2 ELSA-2026-67154-0 Sep 14, 2026
openssl-devel · ol 9 1:3.5.8-1.0.1.el9_8 ELSA-2026-67165-0 Sep 14, 2026
openssl-fips-provider-latest · amzn 2023 1:3.5.8-1.amzn2023.0.1 ALAS2023-2026-2136 Sep 14, 2026
openssl-fips-provider-latest-debuginfo · amzn 2023 1:3.5.8-1.amzn2023.0.1 ALAS2023-2026-2136 Sep 14, 2026
openssl-libs · RHEL 9 1:3.5.8-1.el9_8 RHSA-2026:67165 Sep 19, 2026
openssl-libs · almalinux 10 1:3.5.8-1.el10_2.alma.1 ALSA-2026:67154 Sep 14, 2026
openssl-libs · almalinux 9 1:3.5.8-1.el9_8 ALSA-2026:67165 Sep 14, 2026
openssl-libs · amzn 2023 1:3.5.8-1.amzn2023.0.1 ALAS2023-2026-2136 Sep 14, 2026
openssl-libs · ol 10 1:3.5.8-1.0.1.el10_2 ELSA-2026-67154-0 Sep 14, 2026
openssl-libs · ol 9 1:3.5.8-1.0.1.el9_8 ELSA-2026-67165-0 Sep 14, 2026
openssl-libs-debuginfo · amzn 2023 1:3.5.8-1.amzn2023.0.1 ALAS2023-2026-2136 Sep 14, 2026
openssl-perl · RHEL 9 1:3.5.8-1.el9_8 RHSA-2026:67165 Sep 19, 2026
openssl-perl · almalinux 10 1:3.5.8-1.el10_2.alma.1 ALSA-2026:67154 Sep 14, 2026
openssl-perl · almalinux 9 1:3.5.8-1.el9_8 ALSA-2026:67165 Sep 14, 2026
openssl-perl · amzn 2023 1:3.5.8-1.amzn2023.0.1 ALAS2023-2026-2136 Sep 14, 2026
openssl-perl · ol 10 1:3.5.8-1.0.1.el10_2 ELSA-2026-67154-0 Sep 14, 2026
openssl-perl · ol 9 1:3.5.8-1.0.1.el9_8 ELSA-2026-67165-0 Sep 14, 2026
openssl-provider-legacy · Ubuntu 26.04.1 LTS (resolute) 3.5.5-1ubuntu3.4 openssl-provider-legacy 3.5.5-1ubuntu3.4 Aug 24, 2026
openssl-snapsafe-libs · amzn 2023 1:3.5.8-1.amzn2023.0.1 ALAS2023-2026-2136 Sep 14, 2026
openssl-snapsafe-libs-debuginfo · amzn 2023 1:3.5.8-1.amzn2023.0.1 ALAS2023-2026-2136 Sep 14, 2026

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