CVE-2026-55568
Guzzlephp Guzzle ≤ 7.12.1
Raw vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:NSummary
CVE-2026-55568 is a medium-severity Missing Encryption of Sensitive Data (CWE-311) vulnerability in Guzzlephp Guzzle. Its CVSS base score is 5.9 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Network Sniffing (T1040); ranked at the 1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to CP-12 (Safe Mode) and SC-13 (Cryptographic Protection) — see the control section below for these in your framework.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-38456
Vulnerability Data
Guzzle is an extensible PHP HTTP client. Prior to 7.12.1, in certain configurations, traffic expected to be protected by TLS on the hop to the proxy is transmitted in cleartext. Proxy authentication credentials (the Proxy-Authorization header, proxy userinfo in the…
more
proxy URL, or CURLOPT_PROXYUSERPWD) are sent without encryption, and the CONNECT target host and port for tunneled HTTPS requests are exposed. The built-in cURL handlers (GuzzleHttp\Handler\CurlHandler and GuzzleHttp\Handler\CurlMultiHandler, used by default whenever the PHP cURL extension is available) accept an https:// proxy. libcurl older than 7.50.2 silently treats an https:// proxy as a plaintext http:// proxy. The TLS connection to the proxy is never established, and the proxy leg is cleartext with no error or warning. An application is affected when it sends requests through one of the built-in cURL handlers, configures an https:// proxy expecting the proxy connection itself to be encrypted, and runs with libcurl older than 7.50.2. This vulnerability is fixed in 7.12.1.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
—
—
- 7 hardening rules · 7 OS baselines
V3.2.1V7.4.1V8.3.3V10.3.4
Mitigating Controls (NIST 800-53 r5) AI
SC-13 mandates use of specific cryptography, structurally preventing unencrypted sensitive data.
SC-24 directly requires the system to fail to a known state that preserves security properties, structurally stopping fallback to a less-secure mode.
SC-8 directly requires protecting confidentiality of transmitted information, which structurally eliminates cleartext transmission of sensitive data.
SI-17 mandates explicit fail-safe procedures that activate on indicated failures, preventing the insecure fallback behavior.
CP-12 forces entry into a safe mode on detected conditions, limiting exposure but not covering every failure path.
SC-28 requires cryptographic protection of information at rest, eliminating the storage half of the weakness.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Encryption of data-in-transit directly prevents cleartext transmission while the control also addresses integrity and availability.
PR.DS-01 directly mandates encryption for data-at-rest and therefore prevents CWE-311 mostly for storage, yet the weakness also spans transmission and other contexts that this single at-rest control leaves unaddressed.
Secure-development practices explicitly include designing error and failure handling to remain in a secure state.
Least-privilege policy and enforcement directly counters the permissive-access fallback example in the CWE.
Hardened baselines and configuration management reduce the chance that error paths default to insecure settings.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Specifying encryption and other security technology for network services prevents transmission of sensitive information in cleartext over potentially untrusted channels.
Explicit rules requiring encryption for sensitive information in transit eliminate the weakness of sending data without cryptographic protection.
Specifying communications-security requirements and secure remote-access methods (including encryption expectations) prevents the transmission of sensitive data in cleartext over home or public networks.
Armoured conduits, electromagnetic shielding and locked enclosures make passive eavesdropping on unencrypted traffic traversing the cables more difficult, mitigating exposure of sensitive data in transit.
Explicitly calling for protection of data in transit and at rest, plus secure encryption of communications, drives the implementation of encryption that prevents clear-text exposure of sensitive information.
The control forces an explicit evaluation step before any response, reducing the chance that a failure condition will default to an unsafe open state.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (1 rule)
- V-248525 All OL 8 local disk partitions must implement cryptographic mechanisms to prevent unauthorized disclosure or modification of all information that requires at-rest protection. prevents CWE-311
Oracle Linux 9 (1 rule)
- V-271756 OL 9 local disk partitions must implement cryptographic mechanisms to prevent unauthorized disclosure or modification of all information that requires at rest protection. prevents CWE-311
RHEL 8 (1 rule)
- V-230224 All RHEL 8 local disk partitions must implement cryptographic mechanisms to prevent unauthorized disclosure or modification of all information that requires at rest protection. prevents CWE-311
RHEL 9 (1 rule)
- V-257879 RHEL 9 local disk partitions must implement cryptographic mechanisms to prevent unauthorized disclosure or modification of all information that requires at rest protection. prevents CWE-311
Windows Server 2016 (1 rule)
- V-224843 Systems requiring data at rest protections must employ cryptographic mechanisms to prevent unauthorized disclosure and modification of the information at rest. prevents CWE-311
Windows Server 2019 (1 rule)
- V-205727 Windows Server 2019 systems requiring data at rest protections must employ cryptographic mechanisms to prevent unauthorized disclosure and modification of the information at rest. prevents CWE-311