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24Track

QUIC ACK-only Packet Retention Can Cause Memory Exhaustion

OpenSSL · CVE-2026-63075
0 news outlets0 CERTs and agencies0 researchers

Assessment: Track

SSVC decision points: exploitation none, automatable yes, technical impact partial, deployment high.

What is it?

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 me

Evidence

No coverage recorded yet.

Exploitation

  • Public proof of concept
  • Exploited in the wild
  • Listed as known exploited
CVSS
7.5
EPSS
0.8%
First seen
2 d ago
Status
corroborated

All OpenSSL vulnerabilities