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HIGH

CVE-2026-18798

CVSS v3

7.5

HIGH

EPSS Score

1.5 %

exploit probability, as of 2026-10-20

CISA KEV

No

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • opensslAlmaLinux:10all versions · fixed in 1:3.5.8-1.el10_2.alma.1and 3 other packages
  • opensslAlmaLinux:9all versions · fixed in 1:3.5.8-1.el9_8and 3 other packages

Vendor advisories

  • CVE-2026-18798 Red Hat Product Security151 products fixed · 15 known affected

    openssl: QUIC server may trigger double free when processing INITIAL packet

    edk2-aarch64 as a component of Red Hat Enterprise Linux 10 · edk2-ovmf as a component of Red Hat Enterprise Linux 10 · edk2-tools as a component of Red Hat Enterprise Linux 10

  • RHSA-2026:81201 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: Cost Management Metrics Operator Update

  • RHSA-2026:79357 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: Red Hat Cost Management On-Premise container image update

  • RHSA-2026:79088 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: Red Hat Developer Hub 1.10.5 release.

  • RHSA-2026:72476 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.20.1

  • RHSA-2026:72475 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.20.1

10 more advisories

Full record on NVD

Description

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.

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
2026-08-25
Last Modified
2026-08-25

Frequently asked questions

What is CVE-2026-18798?

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.

Is CVE-2026-18798 actively exploited?

Active exploitation of CVE-2026-18798 has not been confirmed. Its EPSS score was 1.5% on 2026-10-20, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-18798?

CVE-2026-18798 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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