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CVE-2026-9545

Haxx Curl information disclosure

7.5 HIGHPublic exploitEPSS 0.41%
  1. Published3 Jul 2026

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uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate.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

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityNone
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected products

Haxx Curl≥ 8.11.0 < 8.21.0

Remediation

Fixed in
Haxx Curl≥ 8.21.0

References

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Frequently asked

Is CVE-2026-9545 being actively exploited?

CVE-2026-9545 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.41%.

How severe is CVE-2026-9545?

CVE-2026-9545 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.41% probability of exploitation.

Which products are affected by CVE-2026-9545?

Affected products include Haxx Curl.

How do I fix CVE-2026-9545?

Upgrade affected software to a fixed version, for example Haxx Curl 8.21.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-9545 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.