CVE-2026-9545

exposing HTTP/3 early data

cve-program · severity unknownCVSS unknownCheck source for fixed versionsKEV status unknown

Original advisory

cve-program · CVE-2026-9545

Published

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uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate.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.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-9545

Published

curl

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "curl",
                    "product": "curl",
                    "versions": [
                        {
                            "version": "8.11.0",
                            "status": "affected",
                            "versionType": "semver",
                            "lessThan": "8.14.2"
                        },
                        {
                            "version": "8.15.0",
                            "status": "affected",
                            "versionType": "semver",
                            "lessThan": "8.16.1"
                        },
                        {
                            "version": "8.17.0",
                            "status": "affected",
                            "versionType": "semver",
                            "lessThan": "8.20.1"
                        }
                    ],
                    "defaultStatus": "unaffected"
                }

curl

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "curl",
                    "product": "curl",
                    "versions": [
                        {
                            "version": "962097b8dd44ed5b9e7984bc1cdffdbdd566857f",
                            "status": "affected",
                            "versionType": "git",
                            "lessThan": "7b9613fa9b1a5e04301a3920eef58e8138dad05e"
                        }
                    ],
                    "defaultStatus": "unaffected",
                    "repo": "https://github.com/curl/curl.git"
                }

curl

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "curl",
                    "product": "curl",
                    "versions": [
                        {
                            "version": "8.20.0",
                            "status": "affected"
                        },
                        {
                            "version": "8.19.0",
                            "status": "affected"
                        },
                        {
                            "version": "8.18.0",
                            "status": "affected"
                        },
                        {
                            "version": "8.17.0",
                            "status": "affected"
                        },
                        {
                            "version": "8.16.0",
                            "status": "affected"
                        },
                        {
                            "version": "8.15.0",
                            "status": "affected"
                        },
                        {
                            "version": "8.14.1",
                            "status": "affected"
                        },
                        {
                            "version": "8.14.0",
                            "status": "affected"
                        },
                        {
                            "version": "8.13.0",
                            "status": "affected"
                        },
                        {
                            "version": "8.12.1",
                            "status": "affected"
                        },
                        {
                            "version": "8.12.0",
                            "status": "affected"
                        },
                        {
                            "version": "8.11.1",
                            "status": "affected"
                        },
                        {
                            "version": "8.11.0",
                            "status": "affected"
                        }
                    ],
                    "defaultStatus": "unaffected"
                }

Original source record · Cite this exact observation · Complete original publisher JSON