CVE & CISA-KEV Catalog

CVE-2026-9545

UNSCORED
NVD

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uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate.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

How to fix

Remediation Available
curlDebian
Fixed in:8.21.0~rc2-1CVE-2026-9545
curlUbuntu
Fixed in:7.35.0-1ubuntu2.20+esm20USN-8487-1
Fixed in:7.47.0-1ubuntu2.19+esm16USN-8487-1
Fixed in:7.58.0-2ubuntu3.24+esm9USN-8487-1
Fixed in:7.68.0-1ubuntu2.25+esm4USN-8487-1
Fixed in:7.81.0-1ubuntu1.25USN-8487-1
Fixed in:8.5.0-2ubuntu10.10USN-8487-1
Fixed in:8.14.1-2ubuntu1.4USN-8487-1
libcurl3Ubuntu
Fixed in:7.35.0-1ubuntu2.20+esm20USN-8487-1
Fixed in:7.47.0-1ubuntu2.19+esm16USN-8487-1
libcurl3-gnutlsUbuntu
Fixed in:7.35.0-1ubuntu2.20+esm20USN-8487-1
Fixed in:7.47.0-1ubuntu2.19+esm16USN-8487-1
Fixed in:7.58.0-2ubuntu3.24+esm9USN-8487-1
Fixed in:7.68.0-1ubuntu2.25+esm4USN-8487-1
Fixed in:7.81.0-1ubuntu1.25USN-8487-1
libcurl3-nssUbuntu
Fixed in:7.35.0-1ubuntu2.20+esm20USN-8487-1
Fixed in:7.47.0-1ubuntu2.19+esm16USN-8487-1
Fixed in:7.58.0-2ubuntu3.24+esm9USN-8487-1
Fixed in:7.68.0-1ubuntu2.25+esm4USN-8487-1
Fixed in:7.81.0-1ubuntu1.25USN-8487-1
libcurl3t64-gnutlsUbuntu
Fixed in:8.5.0-2ubuntu10.10USN-8487-1
Fixed in:8.14.1-2ubuntu1.4USN-8487-1
libcurl4Ubuntu
Fixed in:7.58.0-2ubuntu3.24+esm9USN-8487-1
Fixed in:7.68.0-1ubuntu2.25+esm4USN-8487-1
Fixed in:7.81.0-1ubuntu1.25USN-8487-1
libcurl4-gnutls-devUbuntu
Fixed in:7.35.0-1ubuntu2.20+esm20USN-8487-1
Fixed in:7.47.0-1ubuntu2.19+esm16USN-8487-1
Fixed in:7.58.0-2ubuntu3.24+esm9USN-8487-1
Fixed in:7.68.0-1ubuntu2.25+esm4USN-8487-1
Fixed in:7.81.0-1ubuntu1.25USN-8487-1
Fixed in:8.5.0-2ubuntu10.10USN-8487-1
Fixed in:8.14.1-2ubuntu1.4USN-8487-1
libcurl4-nss-devUbuntu
Fixed in:7.35.0-1ubuntu2.20+esm20USN-8487-1
Fixed in:7.47.0-1ubuntu2.19+esm16USN-8487-1
Fixed in:7.58.0-2ubuntu3.24+esm9USN-8487-1
Fixed in:7.68.0-1ubuntu2.25+esm4USN-8487-1
Fixed in:7.81.0-1ubuntu1.25USN-8487-1
libcurl4-openssl-devUbuntu
Fixed in:7.35.0-1ubuntu2.20+esm20USN-8487-1
Fixed in:7.47.0-1ubuntu2.19+esm16USN-8487-1
Fixed in:7.58.0-2ubuntu3.24+esm9USN-8487-1
Fixed in:7.68.0-1ubuntu2.25+esm4USN-8487-1
Fixed in:7.81.0-1ubuntu1.25USN-8487-1
Fixed in:8.5.0-2ubuntu10.10USN-8487-1
Fixed in:8.14.1-2ubuntu1.4USN-8487-1
libcurl4t64Ubuntu
Fixed in:8.5.0-2ubuntu10.10USN-8487-1
Fixed in:8.14.1-2ubuntu1.4USN-8487-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3.1 Vector

No CVSS vector data available.

Exploit Intelligence

0.13%probability of exploitation in 30 days
3rdpercentile

Low risk: more likely to be exploited than 3% of all known CVEs.

References

Embed a live status badge for CVE-2026-9545
CVE-2026-9545 severity badge

Markdown

[![CVE-2026-9545](https://tridentstack.com/cve/badge/CVE-2026-9545.svg)](https://tridentstack.com/cve/CVE-2026-9545)

HTML

<a href="https://tridentstack.com/cve/CVE-2026-9545"><img src="https://tridentstack.com/cve/badge/CVE-2026-9545.svg" alt="CVE-2026-9545"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

Start free

This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-03.