{"id":"CVE-2026-63075","state":"PUBLISHED","title":"QUIC ACK-only Packet Retention Can Cause Memory Exhaustion","description":"Issue summary: When OpenSSL processes QUIC traffic from a peer that repeatedly\nsends ack-eliciting packets while not acknowledging ACK-only responses, the\nQUIC stack can retain ACK-only packet metadata for the lifetime of the\nconnection.\n\nImpact summary: A remote peer that can complete a QUIC handshake can\ncause connection-scoped memory growth which may lead to Denial of Service\nthrough memory exhaustion, especially with sustained traffic or many concurrent\nQUIC connections.\n\nCWE: CWE-770: Allocation of Resources Without Limits or Throttling\n\nDescription: When the OpenSSL QUIC stack sends an ACK-only packet,\nthere is no requirement by the QUIC protocol that the peer will acknowledge\nthat ACK-only packet (i.e. it is itself not ack-eliciting). However, the OpenSSL\nimplementation stores the metadata about the ACK frames regardless.\nIn and of itself that's ok, but if a malicious peer establishes a connection, and\nthen drives the connection such that ACK-only packets are forced from the \nOpenSSL implementation peer (i.e., by sending numerous PING frames),\nand then withholding any subsequent acks for ack-eliciting data, like\nlegitimate data, said malicious peer can force inappropriate memory growth\non the OpenSSL peer, potentially leading to a Denial of Service.\n\nThe fix is to ensure that we account for the transmission of the ACK-only\npacket in the packet histories high and low watermark without actually storing\nthe ACK-only packet metadata itself.\n\nFIPS impact: no\nThe OpenSSL FIPS module is not affected as the QUIC code is\noutside the FIPS module boundary.","publishedAt":"2026-08-25T13:00:04.752Z","updatedAt":"2026-08-25T14:36:51.928Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"CISA-ADP"},"assigner":"openssl","products":["OpenSSL OpenSSL"],"affected":[{"vendor":"OpenSSL","product":"OpenSSL","defaultStatus":"unaffected","versions":[{"version":"4.0.0","status":"affected","lessThan":"4.0.2","versionType":"semver"},{"version":"3.6.0","status":"affected","lessThan":"3.6.4","versionType":"semver"},{"version":"3.5.0","status":"affected","lessThan":"3.5.8","versionType":"semver"},{"version":"3.4.0","status":"affected","lessThan":"3.4.7","versionType":"semver"}]}],"references":["https://openssl-library.org/news/secadv/20260825.txt","https://github.com/openssl/openssl/commit/7308946576b12e64b8be53bcf0a120354b2b42bc","https://github.com/openssl/openssl/commit/bf84721c2548351176e367e6de505792f0118dc6","https://github.com/openssl/openssl/commit/7c98d79738549df92868e7dd9be4bbf061eed709","https://github.com/openssl/openssl/commit/c902e5f16d6a9e130e96d3ca6d8f64d71652e393"],"weaknesses":["CWE-770"],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/63xxx/CVE-2026-63075.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-63075","state":"PUBLISHED","datePublished":"2026-08-25T13:00:04.752Z","dateUpdated":"2026-08-25T14:36:51.928Z","assignerShortName":"openssl","assignerOrgId":"3a12439a-ef3a-4c79-92e6-6081a721f1e5","dateReserved":"2026-07-15T13:10:26.188Z"},"containers":{"cna":{"title":"QUIC ACK-only Packet Retention Can Cause Memory Exhaustion","descriptions":[{"lang":"en","value":"Issue summary: When OpenSSL processes QUIC traffic from a peer that repeatedly\nsends ack-eliciting packets while not acknowledging ACK-only responses, the\nQUIC stack can retain ACK-only packet metadata for the lifetime of the\nconnection.\n\nImpact summary: A remote peer that can complete a QUIC handshake can\ncause connection-scoped memory growth which may lead to Denial of Service\nthrough memory exhaustion, especially with sustained traffic or many concurrent\nQUIC connections.\n\nCWE: CWE-770: Allocation of Resources Without Limits or Throttling\n\nDescription: When the OpenSSL QUIC stack sends an ACK-only packet,\nthere is no requirement by the QUIC protocol that the peer will acknowledge\nthat ACK-only packet (i.e. it is itself not ack-eliciting). However, the OpenSSL\nimplementation stores the metadata about the ACK frames regardless.\nIn and of itself that's ok, but if a malicious peer establishes a connection, and\nthen drives the connection such that ACK-only packets are forced from the \nOpenSSL implementation peer (i.e., by sending numerous PING frames),\nand then withholding any subsequent acks for ack-eliciting data, like\nlegitimate data, said malicious peer can force inappropriate memory growth\non the OpenSSL peer, potentially leading to a Denial of Service.\n\nThe fix is to ensure that we account for the transmission of the ACK-only\npacket in the packet histories high and low watermark without actually storing\nthe ACK-only packet metadata itself.\n\nFIPS impact: no\nThe OpenSSL FIPS module is not affected as the QUIC code is\noutside the FIPS module boundary."}],"affected":[{"vendor":"OpenSSL","product":"OpenSSL","defaultStatus":"unaffected","versions":[{"version":"4.0.0","status":"affected","lessThan":"4.0.2","versionType":"semver"},{"version":"3.6.0","status":"affected","lessThan":"3.6.4","versionType":"semver"},{"version":"3.5.0","status":"affected","lessThan":"3.5.8","versionType":"semver"},{"version":"3.4.0","status":"affected","lessThan":"3.4.7","versionType":"semver"}]}],"references":[{"url":"https://openssl-library.org/news/secadv/20260825.txt","name":"OpenSSL Advisory","tags":["vendor-advisory"]},{"url":"https://github.com/openssl/openssl/commit/7308946576b12e64b8be53bcf0a120354b2b42bc","name":"4.0.2 git commit","tags":["patch"]},{"url":"https://github.com/openssl/openssl/commit/bf84721c2548351176e367e6de505792f0118dc6","name":"3.6.4 git commit","tags":["patch"]},{"url":"https://github.com/openssl/openssl/commit/7c98d79738549df92868e7dd9be4bbf061eed709","name":"3.5.8 git commit","tags":["patch"]},{"url":"https://github.com/openssl/openssl/commit/c902e5f16d6a9e130e96d3ca6d8f64d71652e393","name":"3.4.7 git commit","tags":["patch"]}],"metrics":[{"format":"other","other":{"content":{"text":"Low"},"type":"https://openssl-library.org/policies/general/security-policy/"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-770","description":"CWE-770 Allocation of Resources Without Limits or Throttling","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"openssl","orgId":"3a12439a-ef3a-4c79-92e6-6081a721f1e5","dateUpdated":"2026-08-25T13:00:04.752Z"},"credits":[{"lang":"en","type":"reporter","value":"Opal Wright (Trail of Bits)"},{"lang":"en","type":"remediation developer","value":"Neil Horman"}],"datePublic":"2026-08-25T11:36:16.000Z","source":{"discovery":"UNKNOWN"},"x_generator":{"engine":"Vulnogram 0.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"cvssV3_1":{"scope":"UNCHANGED","version":"3.1","baseScore":7.5,"attackVector":"NETWORK","baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","integrityImpact":"NONE","userInteraction":"NONE","attackComplexity":"LOW","availabilityImpact":"HIGH","privilegesRequired":"NONE","confidentialityImpact":"NONE"}},{"other":{"type":"ssvc","content":{"timestamp":"2026-08-25T14:36:48.832724Z","id":"CVE-2026-63075","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-25T14:36:51.928Z"}}]}}}