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Vulnerability record · CVE-2023-27537 · published 30 March 2023

CVE-2023-27537: Haxx libcurl double free vulnerability

Haxx · Libcurl

A double free vulnerability exists in libcurl <8.0.0 when sharing HSTS data between separate "handles". This sharing was introduced without considerations for do this sharing across separate threads but there was no indication of this fact in the documentation. Due to missing mutexes or thread locks, two threads sharing the same HSTS data could end up doing a double-free or use-after-free.

5.9 CVSS 3.1 Medium EPSS 1.9% · top 21.6% CWE-415 · Double free
5.9CVSS 3.1 base score
1.9%EPSS exploitation probability, 30 days
NoNot in CISA KEV
9Affected product versions listed by NVD
6References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

A double free vulnerability exists in libcurl <8.0.0 when sharing HSTS data between separate "handles". This sharing was introduced without considerations for do this sharing across separate threads but there was no indication of this fact in the documentation. Due to missing mutexes or thread locks, two threads sharing the same HSTS data could end up doing a double-free or use-after-free.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

9 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://hackerone.com/reports/1897203 ExploitThird Party Advisory
https://security.gentoo.org/glsa/202310-12 Third Party Advisory
https://security.netapp.com/advisory/ntap-20230420-0010/ Third Party Advisory
https://hackerone.com/reports/1897203 ExploitThird Party Advisory
https://security.gentoo.org/glsa/202310-12 Third Party Advisory
https://security.netapp.com/advisory/ntap-20230420-0010/ Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2023-27537), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.