# CVE-2026-63075: OpenSSL QUIC memory exhaustion denial of service

Source: https://junglewise.ai/threats/cve-2026-63075-openssl-quic-memory-exhaustion-denial-of-service  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-25. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-63075 · Severity: high · CVSS 7.5 · Published 2026-08-25

OpenSSL's QUIC implementation can be forced to accumulate memory indefinitely when processing traffic from a malicious peer. An attacker who can establish a QUIC connection can trigger a denial of service by causing the server to retain excessive metadata in memory, exhausting system resources and disrupting service availability for legitimate users.

Technologies: [OpenSSL](https://junglewise.ai/threats/technologies/openssl). Vendors: [OpenSSL](https://junglewise.ai/threats/vendors/openssl).

## Quick answers

**Is CVE-2026-63075 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-63075 being exploited in the wild.

**How severe is CVE-2026-63075?** High severity, with a CVSS score of 7.5, published 25 August 2026.

**Which products and versions are affected?** OpenSSL <UNKNOWN>.

**Is there a fix for CVE-2026-63075?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-63075 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-63075?** Check whether you run OpenSSL at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

This is an algorithmic resource allocation vulnerability (CWE-770) in OpenSSL's QUIC stack. When the stack sends ACK-only packets, it retains the associated metadata in packet history structures regardless of whether the peer acknowledges them. An attacker can exploit this by completing a QUIC handshake, then sending repeated PING frames to force ACK-only responses from the target, while withholding acknowledgments of ack-eliciting packets. This causes unbounded memory growth on the connection. The vulnerability requires network-level access and successful QUIC handshake completion. The fix involves accounting for ACK-only transmissions in packet history watermarks without storing the packet metadata itself.

## Affected products

- OpenSSL OpenSSL <UNKNOWN>

## Timeline

- 2026-08-25: disclosed

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