Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-9545

CVE-2026-9545HIGH

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   .0041   32.7     —

AFFECTED
  Product  Versions                                    Fixed
  curl     8.11.0 –                                    —
  curl     962097b8dd44ed5b9e7984bc1cdffdbdd566857f –  —
  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)
  Sep 15  EXPLOIT PUBLISHED — CVE-2026-9545 (curl). Public exploit reference added.

CWE-200 · CNA: curl · CVSS v3.1 · 3 references · NVD status: Modified

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uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate.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 — 4 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)
September 15, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-9545 (curl). Public exploit reference added.

Affected

Affected products and packages — 3 rows
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
curl	curl	—	8.11.0	—
curl	curl	—	962097b8dd44ed5b9e7984bc1cdffdbdd566857f	—
curl	curl	—	8.20.0	—

Weaknesses

CWE-200

References (3)

https://curl.se/docs/CVE-2026-9545.html [Patch, Vendor Advisory]
https://curl.se/docs/CVE-2026-9545.json [Vendor Advisory]
https://hackerone.com/reports/3752888 [Exploit, Issue Tracking, Third Party Advisory]

Authoritative record: CVE-2026-9545 at cve.org

Vendors: curl

Weaknesses: CWE-200

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 Sunday, October 4, 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.