CVSS 4.0
8.7 highCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:NCVE-2026-12708 Unbounded HTTP/3 Datagram flow map growth in tokio-quiche
High (8.7) in cloudflare tokio-quiche. EPSS 0.4% estimated probability of exploitation activity in the next 30 days.
Summary
Cloudflare tokio-quiche was found to contain an uncontrolled resource consumption vulnerability in its HTTP/3 DATAGRAM handling. For every previously unseen flow identifier (quarter stream ID) received in a DATAGRAM frame, tokio-quiche creates and retains new, per-flow state. A remote peer can send DATAGRAMs with many distinct identifiers, causing the per-connection flow map and associated channel state to grow without bound.
Impact
Exploitation can exhaust process memory and cause a denial of service. The vulnerable code is used in both client and server configurations, so either role can be affected by a malicious peer. QUIC DATAGRAM support in tokio-quiche is enabled by default through QuicSettings::enable_dgram; applications can disable it by setting this field to false. The vulnerable HTTP/3 path is reachable only when DATAGRAM support is negotiated with the peer. Core quiche and HTTP/3 deployments without DATAGRAM support are not affected.
Mitigation
Disable DATAGRAMs in tokio-quiche’s QuicSettings::enable_dgram.
Remediation
Upgrade to tokio-quiche version 0.23.0 or later. The fixed code creates flow state only for valid DATAGRAM-capable request streams, which are bounded by QUIC’s stream limits. To tolerate packet reordering, servers retain early DATAGRAMs in a bounded, expiring buffer, while clients discard DATAGRAMs for unknown flows.
Severity
- EPSS
- 0.4% estimated probability of exploitation activity in the next 30 days; 30th percentile. Scored 2026-11-13. A forecast for this CVE across the internet, not for your own systems.
- CISA's assessment (SSVC)
- Exploitation: none · Automatable: yes · Technical impact: partial, assessed 2026-11-13. From CISA's Vulnrichment in the CVE List: whether it is exploited, whether exploiting it can be automated, and how much control it gives.
- CWE
- CWE-401 Missing Release of Memory after Effective Lifetime
- Published
- Modified
- Assigned by
- cloudflare (CNA)
- NVD analysis
- Awaiting analysis
- Record from
- the NVD, synced
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Affected
Versions
From the CNA's record in the CVE List.
| Product | Affected |
|---|---|
| Cloudflare tokio-quiche | from 0.0.1 through 0.20.1 |