{"id":"CVE-2026-84784","title":"Issue summary: A malicious remote peer may flood the local QUIC\nstack with NEW_CONNECTION_ID frames by avoiding a limit check on\nhow many connection IDs the remote QUIC stack can use.\n\nImpact summary: The local QUIC stack sends a RETIRE_…","summary":"Issue summary: A malicious remote peer may flood the local QUIC\nstack with NEW_CONNECTION_ID frames by avoiding a limit check on\nhow many connection IDs the remote QUIC stack can use.\n\nImpact summary: The local QUIC stack sends a RETIRE_…","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 >= 4.0.0 < 4.0.3","OpenSSL >= 3.6.0 < 3.6.5","OpenSSL >= 3.5.0 < 3.5.9","OpenSSL >= 3.4.0 < 3.4.8"],"published":"2026-09-29","updated":"2026-09-29","sourceUpdated":"2026-09-29T17:17:11.210","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-84784","references":[{"url":"https://github.com/openssl/openssl/commit/4685c914b0d410b1034f40b547c95bc95e7a380a","label":"openssl-security@openssl.org"},{"url":"https://github.com/openssl/openssl/commit/9a30fe0fba195c14e5b87bf93c0d0fdb70373806","label":"openssl-security@openssl.org"},{"url":"https://github.com/openssl/openssl/commit/dba3c48d653c64fcbc9070a17a0ee2b3e2f3af1f","label":"openssl-security@openssl.org"},{"url":"https://github.com/openssl/openssl/commit/e9e5155833fa968bee50024bf9ca3a185ab599fe","label":"openssl-security@openssl.org"},{"url":"https://openssl-library.org/news/secadv/20260929.txt","label":"openssl-security@openssl.org"}],"tags":["nvd","cve.org"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-09-29T16:43:47.766260Z"},"ingestedAt":"2026-09-29T16:39:33.270Z","slug":"CVE-2026-84784","body":"## Overview\n\nIssue summary: A malicious remote peer may flood the local QUIC\nstack with NEW_CONNECTION_ID frames by avoiding a limit check on\nhow many connection IDs the remote QUIC stack can use.\n\nImpact summary: The local QUIC stack sends a RETIRE_CONN_ID frame\nfor every NEW_CONNECTION_ID frame it receives. The RETIRE_CONN_ID\nframe is dispatched via the Control Frame Queue (CFQ). If the remote\npeer also withholds ACKs, then it can force the local stack\nto allocate ~400MB (depending on ACK delay).\n\nCWE: CWE-770: Allocation of Resources Without Limits or Throttling\n\nDescription: RFC 9000 sections 5.1.1 and 5.1.2 [1] describe the mechanism\nby which a remote peer can notify the local QUIC stack to change the\ndestination connection ID (a.k.a. CID) the local stack uses to\nidentify the connection at the remote peer. Each CID is associated\nwith a sequence number. The sequence number is transmitted\nin NEW_CONNECTION_ID and RETIRE_CONNECTION_ID frames to identify the CID\nwhich is being either associated with a connection or retired.\n\nThe remote peer sends a NEW_CONNECTION_ID frame to let the local stack know\na new CID is being associated with an existing connection. The\nNEW_CONNECTION_ID frame carries the new CID, its sequence number, and the\nretire-prior-to number. The retire-prior-to identifies existing\nCIDs that are to be retired. The local QUIC stack must send a\nRETIRE_CONNECTION_ID for every destination CID whose sequence number\nis less than retire-prior-to. The CID becomes retired after the\nlocal stack receives an ACK for its RETIRE_CONNECTION_ID frame.\n\nAlthough the OpenSSL QUIC stack supports at most one destination CID\nfor every connection, it can be tricked into processing more than\none RETIRE_CONNECTION_ID frame per connection. The OpenSSL QUIC\nstack currently retires the destination CID as soon as it receives\nthe NEW_CONNECTION_ID, while in fact the destination CID must\nbe retired after an ACK for the RETIRE_CONNECTION_ID frame is received.\nCorrecting the flawed logic also fixes the backlog growth.\n\n[1] https://datatracker.ietf.org/doc/html/rfc9000#name-issuing-connection-ids\n\nFIPS impact: no\nThe FIPS module is not affected as the QUIC implementation is outside of\nthe OpenSSL FIPS module boundary.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":212869,"id":"CVE-2026-84784","ts":1790703711988,"field":"cvss","old":null,"new":"7.5"},{"seq":212868,"id":"CVE-2026-84784","ts":1790703711988,"field":"severity","old":"none","new":"high"}]}