Answer in brief
CVE-2026-44434 records a Medium severity (CVSS 5.3) vulnerability in Quicly is vulnerable to stateless reset injection. The current sources do not mark it as known exploited. The current feed maps h2o/quicly (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 5.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps h2o/quicly (generic). Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:a:h2o:quicly:*:*:*:*:*:*:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| h2o/quiclygeneric | <dccf5d4 | dccf5d4 |
Published upstream
Jul 16, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 24, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 17, 2026
Quicly is an IETF QUIC protocol implementation intended primarily for use within the H2O HTTP server. Prior to commit dccf5d4, Quicly was vulnerable to stateless reset injection through lack of packet entry validation. The QUIC protocol is designed to withstand packet injection attacks, once the handshake is complete. Only packets that carry some secret patterns are considered as stateless resets. Quicly allows the peer to share up to 4 such patterns per connection. However, until now, it failed to determine which of the 4 slots that it uses to retain the secret patterns contains a valid entry. As the slots are zero-initialized, the failure meant that, unless the peer advertised 4 of such patterns, an all-zero pattern was treated as a stateless reset.In effect, this allowed an on-path attacker to reset QUIC connections governed by Quicly. This issue has been fixed by commit dccf5d4.
Quoted source text, attributed separately from HOL analysis.