Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.
curl curl — exposing HTTP/3 early data
AV AC PR UI S C I A CVSS EPSS %ile KEV
N L N N U H N N 7.5 .0027 19.1 —
AFFECTED
Product Versions Fixed
curl 8.20.0 – —
TIMELINE
May 26 Reserved by curl
Jul 3 EXPLOIT PUBLISHED — CVE-2026-9545 (curl). Public exploit reference added.
Jul 3 Published (CNA: curl)
Description
In this scenario, libcurl first uses a proper HTTP/3 server for the initial
transfers, and when it makes a second transfer to the same site it has been
replaced by the attacker's impostor machine - without a valid certificate.
When libcurl returns to the hostname the second time with a cached SSL session
(`CURLOPT_SSL_SESSIONID_CACHE` is not disabled) and early data enabled (the
`CURLSSLOPT_EARLYDATA` bit is set in `CURLOPT_SSL_OPTIONS`), libcurl might
send off the second request's bytes on that new connection *before* enforcing
the certificate verification failure. Potentially leaking sensitive
information.
Lifecycle
Complete event history — 3 events, chronological
| Date | Event | Detail |
| May 26, 2026 | Reserved | Reserved by curl |
| July 3, 2026 | EXPLOIT PUBLISHED | EXPLOIT PUBLISHED — CVE-2026-9545 (curl). Public exploit reference added. |
| July 3, 2026 | Published | Published (CNA: curl) |
Affected
Affected products and packages — 1 row
| Vendor | Product / Package | Ecosystem | Version introduced | Fixed |
| curl | curl | — | 8.20.0 | — |
About this page
This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-9545 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.