Vulnerability · Published Aug 25, 2026 · Assigned by openssl
CVE-2026-63075QUIC ACK-only Packet Retention Can Cause Memory Exhaustion
High 7.5
In plain English
A high-severity resource allocation without limits in OpenSSL from OpenSSL. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 47% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Issue summary: When OpenSSL processes QUIC traffic from a peer that repeatedly sends ack-eliciting packets while not acknowledging ACK-only responses, the QUIC stack can retain ACK-only packet metadata for the lifetime of the connection. Impact summary: A remote peer that can complete a QUIC handshake can cause connection-scoped memory growth which may lead to Denial of Service through memory exhaustion, especially with sustained traffic or many concurrent QUIC connections. CWE: CWE-770: Allocation of Resources Without Limits or Throttling Description: When the OpenSSL QUIC stack sends an ACK-only packet, there is no requirement by the QUIC protocol that the peer will acknowledge that ACK-only packet (i.e. it is itself not ack-eliciting). However, the OpenSSL implementation stores the metadata about the ACK frames regardless. In and of itself that's ok, but if a malicious peer establishes a connection, and then drives the connection such that ACK-only packets are forced from the OpenSSL implementation peer (i.e., by sending numerous PING frames), and then withholding any subsequent acks for ack-eliciting data, like legitimate data, said malicious peer can force inappropriate memory growth on the OpenSSL peer, potentially leading to a Denial of Service. The fix is to ensure that we account for the transmission of the ACK-only packet in the packet histories high and low watermark without actually storing the ACK-only packet metadata itself. FIPS impact: no The OpenSSL FIPS module is not affected as the QUIC code is outside the FIPS module boundary.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | openssl | 1:3.5.8-1.el10_2.alma.1 | ALSA-2026:67154 |
| AlmaLinux:9 | openssl | 1:3.5.8-1.el9_8 | ALSA-2026:67165 |
| AlmaLinux:10 | openssl-devel | 1:3.5.8-1.el10_2.alma.1 | ALSA-2026:67154 |
| AlmaLinux:9 | openssl-devel | 1:3.5.8-1.el9_8 | ALSA-2026:67165 |
| AlmaLinux:10 | openssl-libs | 1:3.5.8-1.el10_2.alma.1 | ALSA-2026:67154 |
| AlmaLinux:9 | openssl-libs | 1:3.5.8-1.el9_8 | ALSA-2026:67165 |
| AlmaLinux:10 | openssl-perl | 1:3.5.8-1.el10_2.alma.1 | ALSA-2026:67154 |
| AlmaLinux:9 | openssl-perl | 1:3.5.8-1.el9_8 | ALSA-2026:67165 |
| Alpine:v3.22 | openssl | 3.5.8-r0 | ALPINE-CVE-2026-63075 |
| Alpine:v3.23 | openssl | 3.5.8-r0 | ALPINE-CVE-2026-63075 |
| Alpine:v3.24 | openssl | 3.5.8-r0 | ALPINE-CVE-2026-63075 |
| Debian:13 | openssl | 3.5.7-1~deb13u2 | DEBIAN-CVE-2026-63075 |
| Debian:14 | openssl | 3.6.4-1 | DEBIAN-CVE-2026-63075 |
| Rocky Linux:10 | openssl | 1:3.5.8-1.el10_2 | RLSA-2026:67154 |
| Rocky Linux:9 | openssl | 1:3.5.8-1.el9_8 | RLSA-2026:67165 |
| Ubuntu:26.04:LTS | edk2 | no fix listed | UBUNTU-CVE-2026-63075 |
| Ubuntu:26.10 | edk2 | no fix listed | UBUNTU-CVE-2026-63075 |
| Ubuntu:26.04:LTS | edk2-hwe | no fix listed | UBUNTU-CVE-2026-63075 |
| Ubuntu:26.10 | edk2-hwe | no fix listed | UBUNTU-CVE-2026-63075 |
| Ubuntu:22.04:LTS | openssl | 3.0.2-0ubuntu1.29 | USN-8678-1 |
| Ubuntu:24.04:LTS | openssl | 3.0.13-0ubuntu3.15 | USN-8678-1 |
| Ubuntu:26.04:LTS | openssl | 3.5.5-1ubuntu3.4 | USN-8678-1 |
| Ubuntu:26.04:LTS | openssl | 3.5.5-1ubuntu3.4 | UBUNTU-CVE-2026-63075 |
Affected products (as reported)
Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- OpenSSL Advisory vendor-advisory
- 4.0.2 git commit patch
- 3.6.4 git commit patch
- 3.5.8 git commit patch
- 3.4.7 git commit patch