{"id":"CVE-2026-63075","title":"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.…","summary":"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.…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-770"],"vendor":"openssl","product":"openssl","affected":["openssl >= 3.4.0, < 3.4.7","openssl >= 3.5.0, < 3.5.8","openssl >= 3.6.0, < 3.6.4","openssl >= 4.0.0, < 4.0.2"],"patched":["openssl 4.0.2"],"published":"2026-08-25","updated":"2026-09-11","sourceUpdated":"2026-09-11T21:17:05.403","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-63075","references":[{"url":"https://github.com/openssl/openssl/commit/7308946576b12e64b8be53bcf0a120354b2b42bc","label":"openssl-security@openssl.org"},{"url":"https://github.com/openssl/openssl/commit/7c98d79738549df92868e7dd9be4bbf061eed709","label":"openssl-security@openssl.org"},{"url":"https://github.com/openssl/openssl/commit/bf84721c2548351176e367e6de505792f0118dc6","label":"openssl-security@openssl.org"},{"url":"https://github.com/openssl/openssl/commit/c902e5f16d6a9e130e96d3ca6d8f64d71652e393","label":"openssl-security@openssl.org"},{"url":"https://openssl-library.org/news/secadv/20260825.txt","label":"openssl-security@openssl.org"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63075.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-63075"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2517570"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-63075"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63075"},{"url":"https://access.redhat.com/errata/RHSA-2026:67154"},{"url":"https://access.redhat.com/errata/RHSA-2026:67165"},{"url":"https://access.redhat.com/errata/RHSA-2026:59641"},{"url":"https://access.redhat.com/errata/RHSA-2026:59635"},{"url":"https://access.redhat.com/errata/RHSA-2026:67956"}],"tags":["nvd","csaf","vex","red-hat"],"epss":0.0048,"epssPercentile":0.40463,"ingestedAt":"2026-09-12T00:03:49.031Z","slug":"CVE-2026-63075","body":"## Overview\n\nIssue 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.\n\n## Affected\n\n- `openssl >= 3.4.0, < 3.4.7`\n- `openssl >= 3.5.0, < 3.5.8`\n- `openssl >= 3.6.0, < 3.6.4`\n- `openssl >= 4.0.0, < 4.0.2`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `openssl 4.0.2`\n\n## Vendor advisories\n\n- **RHSA-2026:67154** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10) · released 2026-09-14 · [advisory](https://access.redhat.com/errata/RHSA-2026:67154)\n- **RHSA-2026:67165** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9) · released 2026-09-14 · [advisory](https://access.redhat.com/errata/RHSA-2026:67165)\n- **RHSA-2026:59641** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-08-25 · [advisory](https://access.redhat.com/errata/RHSA-2026:59641)\n- **RHSA-2026:59635** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-08-25 · [advisory](https://access.redhat.com/errata/RHSA-2026:59635)\n- **Red Hat VEX** · Low · affected: Red Hat Developer Hub, Red Hat Enterprise Linux 10, Red Hat JBoss Core Services, Red Hat JBoss Web Server 6, Red Hat JBoss Web Server 7, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Developer Hub, Red Hat Enterprise Linux 10, Red Hat JBoss Core Services, Red Hat JBoss Web Server 6, … · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63075.json)\n- **RHSA-2026:67956** · Red Hat · fixed in: Red Hat Update Infrastructure 5 · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:67956)","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}