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curl CVE-2026-12064

| EUVDEUVD-2026-41502 HIGH
Improper Certificate Validation (CWE-295)
7.5
CVSS 3.1 · Vendor
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Severity by source

Vendor (CNA) PRIMARY
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
vuln.today AI
7.4 HIGH

Requires an active MITM position plus a specific non-default invocation (AC:H); no attacker auth (PR:N); defeated host verification exposes both intercepted data (C:H) and tampering (I:H), with no availability impact.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
4.0 AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
SUSE
7.4 HIGH
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Red Hat
7.5 HIGH
qualitative

Primary rating from Vendor (CNA).

CVSS VectorVendor

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

Lifecycle Timeline

7
Analysis Updated
Jul 06, 2026 - 21:49 vuln.today
v5 (cvss_changed)
Analysis Updated
Jul 06, 2026 - 21:49 vuln.today
v4 (cvss_changed)
Analysis Updated
Jul 06, 2026 - 21:47 vuln.today
v3 (cvss_changed)
Analysis Updated
Jul 06, 2026 - 21:47 vuln.today
v2 (cvss_changed)
Re-analysis Queued
Jul 06, 2026 - 19:22 vuln.today
cvss_changed
CVSS changed
Jul 06, 2026 - 19:22 NVD
7.5 (HIGH)
Analysis Generated
Jun 24, 2026 - 18:31 vuln.today

Description PRE-NVD

Disclosed via oss-security. NVD scoring and full description are pending.

AnalysisAI

SSH host-key verification bypass in curl/libcurl (versions through 8.20.0) lets a network man-in-the-middle silently impersonate an SFTP/SCP server when a user invokes curl with a schemeless URL plus '--proto-default sftp' (or scp). In this specific invocation the command-line tool layer misidentifies the scheme and skips setting CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256 and CURLOPT_SSH_KNOWNHOSTS, while libcurl still honors CURLOPT_DEFAULT_PROTOCOL and completes the connection, so curl connects to an unverified host without any error. Tagged an Authentication Bypass; EPSS is low (0.21%, 11th percentile) and no public exploit was identified at time of analysis.

Technical ContextAI

The affected technology is curl's SSH-based file transfer support (SFTP/SCP), which relies on an underlying SSH library (libssh2/libssh) beneath libcurl. Host authenticity is normally enforced either by known_hosts matching (CURLOPT_SSH_KNOWNHOSTS) or an explicit host public-key fingerprint (CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256). The root cause is a desynchronization between the curl command-line tool and libcurl over how the default protocol is resolved: the tool infers the scheme from the (absent) URL scheme rather than from --proto-default/CURLOPT_DEFAULT_PROTOCOL, so the tool code path that wires up the SSH verification options is never reached, whereas libcurl independently resolves the protocol to SFTP/SCP and proceeds to connect. Although NVD lists CWE as N/A, the behavior is a classic Improper Certificate/Host-Key Validation and Key Exchange Without Entity Authentication class (CWE-295 / CWE-322): the encrypted transport is established but the remote endpoint's identity is never verified.

RemediationAI

Upgrade to a fixed curl/libcurl release as published in the vendor advisory at https://curl.se/docs/CVE-2026-12064.html and the oss-security announcement at https://seclists.org/oss-sec/2026/q2/1012 - no vendor-released patch version is stated in the provided data, so confirm the exact fixed version directly from the curl.se advisory before deploying. Until patched, avoid the vulnerable pattern: do not rely on '--proto-default sftp/scp' with schemeless URLs; instead always supply an explicit scheme in the URL (e.g. sftp://host/path), which routes through the tool code path that installs the host-key options. As a stronger compensating control, pass an explicit host-key fingerprint on every SSH transfer (curl --hostpubsha256 <hash>) or force a known_hosts file (--knownhosts / config), so a missing verification option causes a failure instead of a silent unverified connection; the trade-off is that these must be maintained per host and will break automation if fingerprints rotate. Where feasible, run curl SFTP/SCP transfers only over trusted network paths to reduce MITM exposure.

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
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SLES15-SP6-CHOST-BYOS-Azure Affected
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CVE-2026-12064 vulnerability details – vuln.today

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