QUIC ACK-only Packet Retention Can Cause Memory Exhaustion (CVE-2026-63075) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-63075

QUIC ACK-only Packet Retention Can Cause Memory Exhaustion

Answer in brief

CVE-2026-63075 records a Unknown severity vulnerability in QUIC ACK-only Packet Retention Can Cause Memory Exhaustion. The current sources do not mark it as known exploited. The current feed maps OpenSSL/OpenSSL (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 25, 2026Updated Aug 25, 2026Source checked Aug 25, 2026First seen by HOL Aug 25, 2026Material review Aug 25, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps OpenSSL/OpenSSL (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
OpenSSL/OpenSSLgeneric	>=4.0.0 <4.0.2 \|\| >=3.6.0 <3.6.4 \|\| >=3.5.0 <3.5.8 \|\| >=3.4.0 <3.4.7	4.0.2, 3.6.4, 3.5.8, 3.4.7

Recommended response

Check inventory. Check lockfiles and deployed manifests for OpenSSL/OpenSSL.
Review the reported fix. Update OpenSSL/OpenSSL to 4.0.2 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 25, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.