What is CVE-2026-63075?

CVE-2026-63075 is QUIC ACK-only Packet Retention Can Cause Memory Exhaustion. The supplied enrichment data classifies it as Denial of Service mapped to CWE-770 CWE-770.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Active exploitation is not confirmed from current sources for CVE-2026-63075. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-63075 is not listed in CISA KEV in the supplied enrichment data. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Is there a public exploit?

A public PoC is not confirmed from current sources for CVE-2026-63075. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with Not reported where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-63075 using CVSS null, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

The supplied mitigation guidance says to apply vendor patches and restrict external exposure until fixed. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Prioritize based on EPSS, PoC availability, and external exposure. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

Denial of Service

CVE-2026-63075

CVE-2026-63075 — QUIC ACK-only Packet Retention Can Cause Memory Exhaustion

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.

Published Aug 25, 2026Updated Aug 25, 2026Sources: NVD, OpenSSL (CNA), GitHub, SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Unreported

no source claims exploitation

EPSS

ahead of 0% of scored CVEs

Affects

OpenSSL

4 products listed

CVSS base

Unscored

no source published a base score

Remediation

The vendor's own words where we have them.

Upgrade OpenSSL to a fixed release. Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Prioritize based on EPSS, PoC availability, and external exposure.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
OpenSSL	OpenSSL	4.0.0 to < 4.0.2	Vulnerable
OpenSSL	OpenSSL	3.6.0 to < 3.6.4	Vulnerable
OpenSSL	OpenSSL	3.5.0 to < 3.5.8	Vulnerable
OpenSSL	OpenSSL	3.4.0 to < 3.4.7	Vulnerable

What this weakness leads to

MITRE's own consequences and mitigations for the weakness class — the authority's wording, not guidance derived from the CVSS vector.

MITRE

CWE-770 · Allocation of Resources Without Limits or Throttling

DoS: Resource Consumption (CPU)
DoS: Resource Consumption (Memory)
DoS: Resource Consumption (Other)

Mitigation: Clearly specify the minimum and maximum expectations for capabilities, and dictate which behaviors are acceptable when resource allocation reaches limits.

Weakness & attack patterns

CWE-770

Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.

CAPEC-528 · XML FloodCAPEC-230 · XML Nested PayloadsCAPEC-496 · ICMP FragmentationCAPEC-493 · SOAP Array BlowupCAPEC-487 · ICMP FloodCAPEC-147 · XML Ping of the DeathCAPEC-495 · UDP FragmentationCAPEC-486 · UDP FloodCAPEC-489 · SSL FloodCAPEC-469 · HTTP DoSCAPEC-231 · Oversized Serialized Data PayloadsCAPEC-494 · TCP Fragmentation

T1498.001Network Denial of Service: Direct Network Flood
T1499Endpoint Denial of Service
T1499.003Endpoint Denial of Service: Application Exhaustion Flood

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Initial · CVE published
Aug 25, 2026 · NVD

References

5 on the record

github.com/openssl/openssl/commit/7308946576b12e64b8be53bcf0a120354b2b42bc
Exploit, Third Party Advisory, Mitre
github.com/openssl/openssl/commit/7c98d79738549df92868e7dd9be4bbf061eed709
Exploit, Third Party Advisory, Mitre
github.com/openssl/openssl/commit/bf84721c2548351176e367e6de505792f0118dc6
Exploit, Third Party Advisory, Mitre
github.com/openssl/openssl/commit/c902e5f16d6a9e130e96d3ca6d8f64d71652e393
Exploit, Third Party Advisory, Mitre
openssl-library.org/news/secadv/20260825.txt
Vendor Advisory, Mitre

Elsewhere on this site

OpenSSLevery CVE for this vendor
Denial of Servicesame class
CWE-770other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-63075 is QUIC ACK-only Packet Retention Can Cause Memory Exhaustion, a unscored vulnerability affecting OpenSSL from OpenSSL. The current evidence does not list it in CISA KEV, and the exploit status is: Active exploitation is not confirmed from current sources for CVE-2026-63075. Public exploit evidence is: A public PoC is not confirmed from current sources for CVE-2026-63075. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS null describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.