CVE-2026-12064 (GCVE-0-2026-12064)
Vulnerability from cvelistv5 – Published: 2026-07-03 06:13 – Updated: 2026-07-03 06:13
VLAI?
Title
proto-default skips SSH verification
Summary
When a user invokes curl using a schemeless URL combined with
`--proto-default` sftp (or scp), a disconnect occurs between the tool layer
and libcurl. The tool layer incorrectly infers the URL scheme, which
erroneously bypasses the initialization of critical SSH security options like
CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256 and CURLOPT_SSH_KNOWNHOSTS. Conversely, the
libcurl runtime successfully honors CURLOPT_DEFAULT_PROTOCOL and establishes
the connection via SFTP/SCP as specified. Because the tool layer skipped the
security configuration, these SSH host verification options are silently
omitted, causing curl to connect to an unverified SSH remote host without
throwing an error.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| curl | curl |
Affected:
8.20.0 , ≤ 8.20.0
(semver)
Affected: 8.19.0 , ≤ 8.19.0 (semver) Affected: 8.18.0 , ≤ 8.18.0 (semver) Affected: 8.17.0 , ≤ 8.17.0 (semver) Affected: 8.16.0 , ≤ 8.16.0 (semver) Affected: 8.15.0 , ≤ 8.15.0 (semver) Affected: 8.14.1 , ≤ 8.14.1 (semver) Affected: 8.14.0 , ≤ 8.14.0 (semver) Affected: 8.13.0 , ≤ 8.13.0 (semver) Affected: 8.12.1 , ≤ 8.12.1 (semver) Affected: 8.12.0 , ≤ 8.12.0 (semver) Affected: 8.11.1 , ≤ 8.11.1 (semver) Affected: 8.11.0 , ≤ 8.11.0 (semver) Affected: 8.10.1 , ≤ 8.10.1 (semver) Affected: 8.10.0 , ≤ 8.10.0 (semver) Affected: 8.9.1 , ≤ 8.9.1 (semver) Affected: 8.9.0 , ≤ 8.9.0 (semver) Affected: 8.8.0 , ≤ 8.8.0 (semver) Affected: 8.7.1 , ≤ 8.7.1 (semver) Affected: 8.7.0 , ≤ 8.7.0 (semver) Affected: 8.6.0 , ≤ 8.6.0 (semver) Affected: 8.5.0 , ≤ 8.5.0 (semver) Affected: 8.4.0 , ≤ 8.4.0 (semver) Affected: 8.3.0 , ≤ 8.3.0 (semver) Affected: 8.2.1 , ≤ 8.2.1 (semver) Affected: 8.2.0 , ≤ 8.2.0 (semver) Affected: 8.1.2 , ≤ 8.1.2 (semver) Affected: 8.1.1 , ≤ 8.1.1 (semver) Affected: 8.1.0 , ≤ 8.1.0 (semver) Affected: 8.0.1 , ≤ 8.0.1 (semver) Affected: 8.0.0 , ≤ 8.0.0 (semver) Affected: 7.88.1 , ≤ 7.88.1 (semver) Affected: 7.88.0 , ≤ 7.88.0 (semver) Affected: 7.87.0 , ≤ 7.87.0 (semver) Affected: 7.86.0 , ≤ 7.86.0 (semver) Affected: 7.85.0 , ≤ 7.85.0 (semver) Affected: 7.84.0 , ≤ 7.84.0 (semver) Affected: 7.83.1 , ≤ 7.83.1 (semver) Affected: 7.83.0 , ≤ 7.83.0 (semver) Affected: 7.82.0 , ≤ 7.82.0 (semver) Affected: 7.81.0 , ≤ 7.81.0 (semver) |
Credits
alienowo on hackerone (AntAISecurityLab)
Daniel Stenberg
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"credits": [
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"value": "alienowo on hackerone (AntAISecurityLab)"
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"descriptions": [
{
"lang": "en",
"value": "When a user invokes curl using a schemeless URL combined with\n`--proto-default` sftp (or scp), a disconnect occurs between the tool layer\nand libcurl. The tool layer incorrectly infers the URL scheme, which\nerroneously bypasses the initialization of critical SSH security options like\nCURLOPT_SSH_HOST_PUBLIC_KEY_SHA256 and CURLOPT_SSH_KNOWNHOSTS. Conversely, the\nlibcurl runtime successfully honors CURLOPT_DEFAULT_PROTOCOL and establishes\nthe connection via SFTP/SCP as specified. Because the tool layer skipped the\nsecurity configuration, these SSH host verification options are silently\nomitted, causing curl to connect to an unverified SSH remote host without\nthrowing an error."
}
],
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{
"descriptions": [
{
"description": "CWE-297 Improper Validation of Certificate with Host Mismatch",
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"title": "proto-default skips SSH verification"
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}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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