How severe is CVE-2023-27535?

CVE-2023-27535 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 high, integrity none, and availability none.

Is CVE-2023-27535 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (73rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2023-27535?

CVE-2023-27535 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-2023-27535?

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

When was CVE-2023-27535 published?

CVE-2023-27535 was published on 2023-03-30 and last updated on 2026-06-17.

CVE-2023-27535

CVE-2023-27535 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-287.

Key facts

Severity: Medium (CVSS 3.x base score 5.9)
EPSS exploit prediction: 2% (73rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-287
Affected product: Haxx Libcurl
Published: 2023-03-30
Last modified: 2026-06-17

Description

An authentication bypass vulnerability exists in libcurl <8.0.0 in the FTP connection reuse feature that can result in wrong credentials being used during subsequent transfers. Previously created connections are kept in a connection pool for reuse if they match the current setup. However, certain FTP settings such as CURLOPT_FTP_ACCOUNT, CURLOPT_FTP_ALTERNATIVE_TO_USER, CURLOPT_FTP_SSL_CCC, and CURLOPT_USE_SSL were not included in the configuration match checks, causing them to match too easily. This could lead to libcurl using the wrong credentials when performing a transfer, potentially allowing unauthorized access to sensitive information.

Frequently asked questions

What is CVE-2023-27535?: An authentication bypass vulnerability exists in libcurl <8.0.0 in the FTP connection reuse feature that can result in wrong credentials being used during subsequent transfers. Previously created connections are kept in a connection pool for reuse if they match the current setup. However, certain FTP settings such as CURLOPT_FTP_ACCOUNT, CURLOPT_FTP_ALTERNATIVE_TO_USER, CURLOPT_FTP_SSL_CCC, and CURLOPT_USE_SSL were not included in the configuration match checks, causing them to match too easily. This could lead to libcurl using the wrong credentials when performing a transfer, potentially allowing unauthorized access to sensitive information.
How severe is CVE-2023-27535?: CVE-2023-27535 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 high, integrity none, and availability none.
Is CVE-2023-27535 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (73rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-27535?: CVE-2023-27535 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-2023-27535?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2023-27535 published?: CVE-2023-27535 was published on 2023-03-30 and last updated on 2026-06-17.

References

Affected products (11)

cpe:2.3:a:haxx:libcurl:*:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:36:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:a:netapp:active_iq_unified_manager:-:*:*:*:*:vmware_vsphere:*:*
cpe:2.3:a:netapp:ontap_9:-:*:*:*:*:*:*:*
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:*:*:*:*:*:*:*

More vulnerabilities in Haxx Libcurl

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CVE-2017-8816 — Critical (CVSS 9.8): The NTLM authentication feature in curl and libcurl before 7.57.0 on 32-bit platforms allows attackers to cause a…
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Other CWE-287 (Improper Authentication) vulnerabilities

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CVE-2026-10611 — Critical (CVSS 10.0): An authentication bypass vulnerability exists in MISP when LDAP mixed authentication is enabled with OTP enforcement.…
CVE-2026-47280 — Critical (CVSS 10.0): Improper authentication in Azure Resource Manager (ARM) allows an unauthorized attacker to elevate privileges over a…
CVE-2026-42822 — Critical (CVSS 10.0): Improper authentication in Azure Local Disconnected Operations allows an unauthorized attacker to elevate privileges…
CVE-2026-20182 — Critical (CVSS 10.0): May 2026: This security advisory provides the details and fix information for a vulnerability that was discovered and…

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