exposing HTTP/3 early data

Answer in brief

CVE-2026-9545 records a High severity (CVSS 7.5) vulnerability in exposing HTTP/3 early data. The current sources do not mark it as known exploited. The current feed maps curl/curl (generic), curl/curl (generic), curl/curl (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jul 3, 2026Updated Sep 15, 2026Source checked Sep 15, 2026First seen by HOL Jul 3, 2026Material review Sep 15, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.5
Exploitation: Not marked as known exploited
Affected software: 3 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 7.5. 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.

Affected scope and exposure questions

The current feed maps curl/curl (generic), curl/curl (generic), curl/curl (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
curl/curlgeneric	>=8.11.0 <8.14.2 \|\| >=8.15.0 <8.16.1 \|\| >=8.17.0 <8.20.1	8.14.2, 8.16.1, 8.20.1
curl/curlgeneric	>=962097b8dd44ed5b9e7984bc1cdffdbdd566857f <7b9613fa9b1a5e04301a3920eef58e8138dad05e	7b9613fa9b1a5e04301a3920eef58e8138dad05e
curl/curlgeneric	8.20.0 \|\| 8.19.0 \|\| 8.18.0 \|\| 8.17.0 \|\| 8.16.0 \|\| 8.15.0 \|\| 8.14.1 \|\| 8.14.0 \|\| 8.13.0 \|\| 8.12.1 \|\| 8.12.0 \|\| 8.11.1 \|\| 8.11.0	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for curl/curl, curl/curl, curl/curl.
Review the reported fix. Update curl/curl to 8.14.2; curl/curl to 7b9613fa9b1a5e04301a3920eef58e8138dad05e if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jul 3, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 15, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Jul 3, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.