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CVE-2026-9545

exposing HTTP/3 early data

High7.5EPSS 0.41%
Published
Updated
Reserved
Assigned by
curl

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uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate.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

Scores

CVSS scores of CVE-2026-9545, by who scored it
Scored byCVSSScoreVector
CISA-ADPADP (enrichment)3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVDNVD · Modified3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS (exploitation in 30 days)
0.41% · top 65% of all CVEs (6 Nov 2026)
CISA SSVC
Exploitation: poc · Automatable: yes · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.

Weakness

Affected products

  • curl · curl

    • affected 8.11.0 – < 8.14.2
    • affected 8.15.0 – < 8.16.1
    • affected 8.17.0 – < 8.20.1

  • curl · curl

    • affected 962097b8dd44ed5b9e7984bc1cdffdbdd566857f – < 7b9613fa9b1a5e04301a3920eef58e8138dad05e

  • curl · curl

    • affected 8.20.0
    • affected 8.19.0
    • affected 8.18.0
    • affected 8.17.0
    • affected 8.16.0
    • affected 8.15.0
    • affected 8.14.1
    • affected 8.14.0
    • affected 8.13.0
    • affected 8.12.1
    • affected 8.12.0
    • affected 8.11.1
    • affected 8.11.0

References (3)

Sources

The same CVE in the primary databases and aggregators, to check against.

Badge for a README or a ticket

CVE-2026-9545 badge
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Record last updated .