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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
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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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.