How severe is CVE-2023-27537?

CVE-2023-27537 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2023-27537 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (77th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2023-27537?

CVE-2023-27537 primarily affects Haxx Libcurl. In total, 11 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2023-27537?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2023-27537 published?

CVE-2023-27537 was published on 2023-03-30 and last updated on 2026-06-17.

CVE-2023-27537

CVE-2023-27537 is a medium-severity vulnerability in Haxx Libcurl with a CVSS 3.x base score of 5.9. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-415.

Key facts

Severity: Medium (CVSS 3.x base score 5.9)
EPSS exploit prediction: 2% (77th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-415
Affected product: Haxx Libcurl
Published: 2023-03-30
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2023-27537?: 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.
How severe is CVE-2023-27537?: CVE-2023-27537 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2023-27537 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (77th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-27537?: CVE-2023-27537 primarily affects Haxx Libcurl. In total, 11 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2023-27537?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2023-27537 published?: CVE-2023-27537 was published on 2023-03-30 and last updated on 2026-06-17.

References

Affected products (11)

cpe:2.3:a:haxx:libcurl:7.88.0:*:*:*:*:*:*:*
cpe:2.3:a:haxx:libcurl:7.88.1:*:*:*:*:*:*:*
cpe:2.3:a:netapp:active_iq_unified_manager:-:*:*:*:*:vmware_vsphere:*:*
cpe:2.3:a:netapp:clustered_data_ontap:9.0:-:*:*:*:*:*:*
cpe:2.3:o:broadcom:brocade_fabric_operating_system_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h300s_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h500s_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h700s_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h410s_firmware:-:*:*:*:*:*:*:*
cpe:2.3:a:splunk:universal_forwarder:*:*:*:*:*:*:*:*
cpe:2.3:a:splunk:universal_forwarder:9.1.0:*:*:*:*:*:*:*

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Other CWE-415 (Double Free) vulnerabilities

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CVE-2020-37239 — Critical (CVSS 9.8): libbabl 0.1.62 contains a broken double free detection vulnerability that allows attackers to bypass memory safety…
CVE-2026-43011 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: net/x25: Fix potential double free of skb When…
CVE-2026-31609 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: smb: client: avoid double-free in…
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