CVE-2026-21428
cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to version 0.30.0, the ``write_headers`` function does not check for CR & LF characters in user supplied headers, allowing untrusted header value to escape header lines. This vulnerability allows attackers to add extra headers, modify request body unexpectedly & trigger an SSRF attack. When combined with a server that supports http1.1 pipelining (springboot, python twisted etc), this can be used for server side request forgery (SSRF). Version 0.30.0 fixes this issue.
Vulnerability Summary
CVSS v3 Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS Score (Exploitation Probability)
This vulnerability has a 0.01% probability of being exploited in the next 30 days, ranking higher than 3% of all scored CVEs.
CWE Classification
Related Vulnerabilities
Same Weakness Type(CWE-93)
Vulnerability in the Oracle Configurator product of Oracle E-Business Suite (component: Runtime UI). Supported versions that are affected are 12.2.3-12.2.14. Easily exploitable vulnerability allows unauthenticated attacker with network access via HTTP to compromise Oracle Configurator. Successful attacks of this vulnerability can result in unauthorized access to critical data or complete access to all Oracle Configurator accessible data. CVSS 3.1 Base Score 7.5 (Confidentiality impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).
Possible CRLF injection allowing HTTP response splitting attacks for sites which use mod_userdir. This issue was mitigated by changes made in 2.4.25 and 2.2.32 which prohibit CR or LF injection into the "Location" or other outbound header key or value. Fixed in Apache HTTP Server 2.4.25 (Affected 2.4.1-2.4.23). Fixed in Apache HTTP Server 2.2.32 (Affected 2.2.0-2.2.31).
Similar SeverityHIGH
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OpenClaw before 2026.4.22 contains a server-side request forgery vulnerability in the Zalo plugin's sendPhoto function that fails to validate outbound photo URLs through the SSRF guard. Attackers can bypass SSRF protection by providing malicious photo URLs to the Zalo Bot API, enabling unauthorized access to internal resources.
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