CVE-2026-63075 (GCVE-0-2026-63075)

Vulnerability from cvelistv5 – Published: 2026-08-25 13:00 – Updated: 2026-08-25 14:36
VLAI
Title
QUIC ACK-only Packet Retention Can Cause Memory Exhaustion
Summary
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.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-25 14:36 UTC
CWE
  • CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
openssl CNA under the mitre root
CNA scorecard B 78/100 over 43 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
OpenSSL OpenSSL Affected: 4.0.0 , < 4.0.2 (semver)
Affected: 3.6.0 , < 3.6.4 (semver)
Affected: 3.5.0 , < 3.5.8 (semver)
Affected: 3.4.0 , < 3.4.7 (semver)
guessed Create a notification for this product.
Date Public
2026-08-25 11:36
Credits
Opal Wright (Trail of Bits) Neil Horman
Show details on NVD website
To clipboard 

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                  "value": "Issue summary: When OpenSSL processes QUIC traffic from a peer that repeatedly\u003cbr\u003esends ack-eliciting packets while not acknowledging ACK-only responses, the\u003cbr\u003eQUIC stack can retain ACK-only packet metadata for the lifetime of the\u003cbr\u003econnection.\u003cbr\u003e\u003cbr\u003eImpact summary: A remote peer that can complete a QUIC handshake can\u003cbr\u003ecause connection-scoped memory growth which may lead to Denial of Service\u003cbr\u003ethrough memory exhaustion, especially with sustained traffic or many concurrent\u003cbr\u003eQUIC connections.\u003cbr\u003e\u003cbr\u003eCWE: CWE-770: Allocation of Resources Without Limits or Throttling\u003cbr\u003e\u003cbr\u003eDescription: When the OpenSSL QUIC stack sends an ACK-only packet,\u003cbr\u003ethere is no requirement by the QUIC protocol that the peer will acknowledge\u003cbr\u003ethat ACK-only packet (i.e. it is itself not ack-eliciting). However, the OpenSSL\u003cbr\u003eimplementation stores the metadata about the ACK frames regardless.\u003cbr\u003eIn and of itself that\u0027s ok, but if a malicious peer establishes a connection, and\u003cbr\u003ethen drives the connection such that ACK-only packets are forced from the \u003cbr\u003eOpenSSL implementation peer (i.e., by sending numerous PING frames),\u003cbr\u003eand then withholding any subsequent acks for ack-eliciting data, like\u003cbr\u003elegitimate data, said malicious peer can force inappropriate memory growth\u003cbr\u003eon the OpenSSL peer, potentially leading to a Denial of Service.\u003cbr\u003e\u003cbr\u003eThe fix is to ensure that we account for the transmission of the ACK-only\u003cbr\u003epacket in the packet histories high and low watermark without actually storing\u003cbr\u003ethe ACK-only packet metadata itself.\u003cbr\u003e\u003cbr\u003eFIPS impact: no\u003cbr\u003eThe OpenSSL FIPS module is not affected as the QUIC code is\u003cbr\u003eoutside 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\u0027s 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": {
            "dateUpdated": "2026-08-25T13:00:04.752Z",
            "orgId": "3a12439a-ef3a-4c79-92e6-6081a721f1e5",
            "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": "3a12439a-ef3a-4c79-92e6-6081a721f1e5",
        "assignerShortName": "openssl",
        "cveId": "CVE-2026-63075",
        "datePublished": "2026-08-25T13:00:04.752Z",
        "dateReserved": "2026-07-15T13:10:26.188Z",
        "dateUpdated": "2026-08-25T14:36:51.928Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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