{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "OpenSSL",
          "vendor": "OpenSSL",
          "versions": [
            {
              "lessThan": "4.0.2",
              "status": "affected",
              "version": "4.0.0",
              "versionType": "semver"
            },
            {
              "lessThan": "3.6.4",
              "status": "affected",
              "version": "3.6.0",
              "versionType": "semver"
            },
            {
              "lessThan": "3.5.8",
              "status": "affected",
              "version": "3.5.0",
              "versionType": "semver"
            },
            {
              "lessThan": "3.4.7",
              "status": "affected",
              "version": "3.4.0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "reporter",
          "value": "Opal Wright (Trail of Bits)"
        },
        {
          "lang": "en",
          "type": "remediation developer",
          "value": "Neil Horman"
        }
      ],
      "datePublic": "2026-08-25T13:36:16+02:00",
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "Issue summary: When OpenSSL processes QUIC traffic from a peer that repeatedly<br>sends ack-eliciting packets while not acknowledging ACK-only responses, the<br>QUIC stack can retain ACK-only packet metadata for the lifetime of the<br>connection.<br><br>Impact summary: A remote peer that can complete a QUIC handshake can<br>cause connection-scoped memory growth which may lead to Denial of Service<br>through memory exhaustion, especially with sustained traffic or many concurrent<br>QUIC connections.<br><br>CWE: CWE-770: Allocation of Resources Without Limits or Throttling<br><br>Description: When the OpenSSL QUIC stack sends an ACK-only packet,<br>there is no requirement by the QUIC protocol that the peer will acknowledge<br>that ACK-only packet (i.e. it is itself not ack-eliciting). However, the OpenSSL<br>implementation stores the metadata about the ACK frames regardless.<br>In and of itself that's ok, but if a malicious peer establishes a connection, and<br>then drives the connection such that ACK-only packets are forced from the <br>OpenSSL implementation peer (i.e., by sending numerous PING frames),<br>and then withholding any subsequent acks for ack-eliciting data, like<br>legitimate data, said malicious peer can force inappropriate memory growth<br>on the OpenSSL peer, potentially leading to a Denial of Service.<br><br>The fix is to ensure that we account for the transmission of the ACK-only<br>packet in the packet histories high and low watermark without actually storing<br>the ACK-only packet metadata itself.<br><br>FIPS impact: no<br>The OpenSSL FIPS module is not affected as the QUIC code is<br>outside the FIPS module boundary."
            }
          ],
          "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."
        }
      ],
      "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": {
        "orgId": "00000000-0000-4000-9000-000000000000",
        "shortName": "openssl"
      },
      "references": [
        {
          "name": "OpenSSL Advisory",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://openssl-library.org/news/secadv/20260825.txt"
        },
        {
          "name": "4.0.2 git commit",
          "tags": [
            "patch"
          ],
          "url": "https://github.com/openssl/openssl/commit/7308946576b12e64b8be53bcf0a120354b2b42bc"
        },
        {
          "name": "3.6.4 git commit",
          "tags": [
            "patch"
          ],
          "url": "https://github.com/openssl/openssl/commit/bf84721c2548351176e367e6de505792f0118dc6"
        },
        {
          "name": "3.5.8 git commit",
          "tags": [
            "patch"
          ],
          "url": "https://github.com/openssl/openssl/commit/7c98d79738549df92868e7dd9be4bbf061eed709"
        },
        {
          "name": "3.4.7 git commit",
          "tags": [
            "patch"
          ],
          "url": "https://github.com/openssl/openssl/commit/c902e5f16d6a9e130e96d3ca6d8f64d71652e393"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "QUIC ACK-only Packet Retention Can Cause Memory Exhaustion",
      "x_generator": {
        "engine": "Vulnogram 0.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "00000000-0000-4000-9000-000000000000",
    "cveId": "CVE-2026-63075",
    "requesterUserId": "00000000-0000-4000-9000-000000000000",
    "serial": 1,
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1"
}