CVE-2026-18798: QUIC Server May Trigger Double Free When Processing INITIAL Packet
Vulnerability summary
CVE-2026-18798 is a high (CVSS 7.5) Double Free vulnerability in openssl. EPSS estimates a 1.70% chance of exploitation in the next 30 days, higher than 77.2% of scored vulnerabilities.
Severe, CVSS 7.5 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 2% (FIRST, 03-11-2026)
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 11 · Related 6Timeline
- 25-08-2026PublishedVulnerability first disclosed.
- 25-08-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
7 scores · 7 sources · 1 version- OSV · AlpineEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · ChainguardEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · WolfiEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
1.70%
Chance of exploitation in the next 30 days
Percentile
77%
Versus all other CVEs
30-day change
Increase +0.16 pp
From 1.54% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Chainguard12 products
- eco-python-openssl-4< 4.0.2-r0
- eco-python-openssl-4-pyca< 4.0.2-r0
- eco-python-openssl-4-pyca-dev< 4.0.2-r0
- openssl-3.5< 3.5.8-r0
- openssl-3.5-libcrypto< 3.5.8-r0
Ubuntu4 products
- edk2All versions (No fix recorded)
- edk2-hweAll versions (No fix recorded)
- nodejsAll versions (No fix recorded)
- openssl< 3.5.5-1ubuntu3.4
Wolfi3 products
- openssl-4.0< 4.0.2-r0
- openssl-4.0-libcrypto< 4.0.2-r0
- openssl-4.0-libssl< 4.0.2-r0
Alpine1 product
- openssl≥ 3.5.0, < 3.5.8-r0
Debian1 product
- openssl< 3.5.7-1~deb13u2 | < 3.6.4-1
Openssl1 product
- openssl≥ 3.5.0, < 3.5.8 | ≥ 3.6.0, < 3.6.4 | ≥ 4.0.0, < 4.0.2
6 vendors · 22 products
