CVE-2026-84784

HIGHPre-NVD 7.57.5—
EchelonGraph scoreHIGH confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-09-29. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
Trending — Patch released this week
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 7.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Issue summary: A malicious remote peer may flood the local QUIC stack with NEW_CONNECTION_ID frames by avoiding a limit check on how many connection IDs the remote QUIC stack can use.

Impact summary: The local QUIC stack sends a RETIRE_CONN_ID frame for every NEW_CONNECTION_ID frame it receives. The RETIRE_CONN_ID frame is dispatched via the Control Frame Queue (CFQ). If the remote peer also withholds ACKs, then it can force the local stack to allocate ~400MB (depending on ACK delay).

CWE: CWE-770: Allocation of Resources Without Limits or Throttling

Description: RFC 9000 sections 5.1.1 and 5.1.2 [1] describe the mechanism by which a remote peer can notify the local QUIC stack to change the destination connection ID (a.k.a. CID) the local stack uses to identify the connection at the remote peer. Each CID is associated with a sequence number. The sequence number is transmitted in NEW_CONNECTION_ID and RETIRE_CONNECTION_ID frames to identify the CID which is being either associated with a connection or retired.

The remote peer sends a NEW_CONNECTION_ID frame to let the local stack know a new CID is being associated with an existing connection. The NEW_CONNECTION_ID frame carries the new CID, its sequence number, and the retire-prior-to number. The retire-prior-to identifies existing CIDs that are to be retired. The local QUIC stack must send a RETIRE_CONNECTION_ID for every destination CID whose sequence number is less than retire-prior-to. The CID becomes retired after the local stack receives an ACK for its RETIRE_CONNECTION_ID frame.

Although the OpenSSL QUIC stack supports at most one destination CID for every connection, it can be tricked into processing more than one RETIRE_CONNECTION_ID frame per connection. The OpenSSL QUIC stack currently retires the destination CID as soon as it receives the NEW_CONNECTION_ID, while in fact the destination CID must be retired after an ACK for the RETIRE_CONNECTION_ID frame is received. Correcting the flawed logic also fixes the backlog growth.

[1] https://datatracker.ietf.org/doc/html/rfc9000#name-issuing-connection-ids

FIPS impact: no The FIPS module is not affected as the QUIC implementation is outside of the OpenSSL FIPS module boundary.

CVSS v3
7.5
EG Score
7.5HIGHhigh confidence
EG Risk
49
EG Risk 49/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity75% × 45%
Exploitation0% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.4%
EPSS %ILE
32nd
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 29, 2026

Last Modified

September 29, 2026

Advisory Details (5)

Auto-updated Sep 29, 2026
Patch available. Sources: github_commit.
github_commit

commit 9a30fe0fba19 (openssl/openssl)

Fix landed in openssl/openssl commit 9a30fe0fba19 — awaiting tagged release

https://github.com/openssl/openssl/commit/9a30fe0fba195c14e5b87bf93c0d0fdb70373806
github_commit

commit dba3c48d653c (openssl/openssl)

Fix landed in openssl/openssl commit dba3c48d653c — awaiting tagged release

https://github.com/openssl/openssl/commit/dba3c48d653c64fcbc9070a17a0ee2b3e2f3af1f
github_commit

commit 4685c914b0d4 (openssl/openssl)

Fix landed in openssl/openssl commit 4685c914b0d4 — awaiting tagged release

https://github.com/openssl/openssl/commit/4685c914b0d410b1034f40b547c95bc95e7a380a
github_commit

commit e9e5155833fa (openssl/openssl)

Fix landed in openssl/openssl commit e9e5155833fa — awaiting tagged release

https://github.com/openssl/openssl/commit/e9e5155833fa968bee50024bf9ca3a185ab599fe
generic
https://openssl-library.org/news/secadv/20260929.txt

Vendor Advisories for CVE-2026-84784(4)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(3)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuopenssl-provider-legacy (3.5.5-1ubuntu3.6) @ resolute2026-10-04ubuntu
redhatopenssl3-main-3.5.9-0.1.hum12026-09-30redhat
redhatopenssl-main-3.5.9-0.1.hum12026-09-30redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 34× in last 7d / 34× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-04 03:03 UTCVendor advisory
  2. 2026-10-04 03:03 UTCGHSA enrichment
  3. 2026-10-03 15:50 UTCEG score recompute
  4. 2026-10-03 15:50 UTCVendor advisory
  5. 2026-10-03 15:49 UTCGHSA enrichment
  6. 2026-10-03 14:26 UTCEPSS rescore
  7. 2026-10-03 04:33 UTCEG score recompute
  8. 2026-10-03 04:33 UTCVendor advisory
  9. 2026-10-03 04:33 UTCGHSA enrichment
  10. 2026-10-02 17:57 UTCEPSS rescore
  11. 2026-10-02 17:20 UTCVendor advisory
  12. 2026-10-02 17:19 UTCGHSA enrichment
  13. 2026-10-02 06:04 UTCEG score recompute
  14. 2026-10-02 06:04 UTCVendor advisory
  15. 2026-10-02 06:04 UTCGHSA enrichment
  16. 2026-10-01 19:50 UTCEPSS rescore
  17. 2026-10-01 18:51 UTCVendor advisory
  18. 2026-10-01 18:51 UTCGHSA enrichment
  19. 2026-10-01 07:38 UTCVendor advisory
  20. 2026-10-01 07:38 UTCGHSA enrichment
  21. 2026-09-30 20:25 UTCEG score recompute
  22. 2026-09-30 20:25 UTCVendor advisory
  23. 2026-09-30 20:25 UTCGHSA enrichment
  24. 2026-09-30 15:04 UTCEPSS rescore
  25. 2026-09-30 09:11 UTCVendor advisory
Show 9 more
  1. 2026-09-30 09:11 UTCGHSA enrichment
  2. 2026-09-29 21:57 UTCEG score recompute
  3. 2026-09-29 21:57 UTCVendor advisory
  4. 2026-09-29 21:57 UTCGHSA enrichment
  5. 2026-09-29 16:53 UTCEG score recompute▲ 7.50
  6. 2026-09-29 16:53 UTCMITRE cvelistV5CVSS v3 → 7.5 · severity → HIGH
  7. 2026-09-29 16:24 UTCNVD update
  8. 2026-09-29 15:38 UTCEG score recompute
  9. 2026-09-29 15:38 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-84784?
CVE-2026-84784 is a high vulnerability published on September 29, 2026. Issue summary: A malicious remote peer may flood the local QUIC stack with NEWCONNECTIONID frames by avoiding a limit check on how many connection IDs the remote QUIC stack can use. Impact summary: The local QUIC stack sends a RETIRECONNID frame for every NEWCONNECTIONID frame it receives. The…
When was CVE-2026-84784 disclosed?
CVE-2026-84784 was first published on September 29, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-84784 actively exploited?
CVE-2026-84784 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (32nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-84784?
CVE-2026-84784 has a CVSS v3.1 base score of 7.5 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-84784?
A fix for CVE-2026-84784 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-84784 are linked in the Vendor Advisories panel on this page.

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