# CVE-2023-27537: curl: A double free vulnerability exists in libcurl <8.0.0 when sharing HSTS data between separate "handles"

CVE-2023-27537 is fixed in 10 products on 1 platform, first by DEBIAN-CVE-2023-27537, released March 30, 2023. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2023-27537
- Priority: Routine
- CVSS: 5.9 (medium)
- EPSS: 0.0190
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 30, 2023

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | curl Debian 12.15 (bookworm) | 7.88.1-7 | [DEBIAN-CVE-2023-27537](https://patchblox.com/security/data/fix/linux/debian-cve-2023-27537.md) | Mar 30, 2023 |
| Linux | curl Debian 13.5 (trixie) | 7.88.1-7 | [DEBIAN-CVE-2023-27537](https://patchblox.com/security/data/fix/linux/debian-cve-2023-27537.md) | Mar 30, 2023 |
| Linux | curl Debian 14 | 7.88.1-7 | [DEBIAN-CVE-2023-27537](https://patchblox.com/security/data/fix/linux/debian-cve-2023-27537.md) | Mar 30, 2023 |
| Linux | curl amzn 2023 | 8.0.1-1.amzn2023 | [ALAS2023-2023-193](https://patchblox.com/security/data/fix/linux/alas2023-2023-193.md) | Jun 5, 2023 |
| Linux | curl-debuginfo amzn 2023 | 8.0.1-1.amzn2023 | [ALAS2023-2023-193](https://patchblox.com/security/data/fix/linux/alas2023-2023-193.md) | Jun 5, 2023 |
| Linux | curl-debugsource amzn 2023 | 8.0.1-1.amzn2023 | [ALAS2023-2023-193](https://patchblox.com/security/data/fix/linux/alas2023-2023-193.md) | Jun 5, 2023 |
| Linux | curl-minimal amzn 2023 | 8.0.1-1.amzn2023 | [ALAS2023-2023-193](https://patchblox.com/security/data/fix/linux/alas2023-2023-193.md) | Jun 5, 2023 |
| Linux | curl-minimal-debuginfo amzn 2023 | 8.0.1-1.amzn2023 | [ALAS2023-2023-193](https://patchblox.com/security/data/fix/linux/alas2023-2023-193.md) | Jun 5, 2023 |
| Linux | libcurl amzn 2023 | 8.0.1-1.amzn2023 | [ALAS2023-2023-193](https://patchblox.com/security/data/fix/linux/alas2023-2023-193.md) | Jun 5, 2023 |
| Linux | libcurl-debuginfo amzn 2023 | 8.0.1-1.amzn2023 | [ALAS2023-2023-193](https://patchblox.com/security/data/fix/linux/alas2023-2023-193.md) | Jun 5, 2023 |
| Linux | libcurl-devel amzn 2023 | 8.0.1-1.amzn2023 | [ALAS2023-2023-193](https://patchblox.com/security/data/fix/linux/alas2023-2023-193.md) | Jun 5, 2023 |
| Linux | libcurl-minimal amzn 2023 | 8.0.1-1.amzn2023 | [ALAS2023-2023-193](https://patchblox.com/security/data/fix/linux/alas2023-2023-193.md) | Jun 5, 2023 |
| Linux | libcurl-minimal-debuginfo amzn 2023 | 8.0.1-1.amzn2023 | [ALAS2023-2023-193](https://patchblox.com/security/data/fix/linux/alas2023-2023-193.md) | Jun 5, 2023 |

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Data as of 2026-11-09T07:25:28Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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