CVE-2026-28435
Published: 04 March 2026
Summary
CVE-2026-28435 is a high-severity Uncontrolled Resource Consumption (CWE-400) vulnerability in Yhirose Cpp-Httplib. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 23.7th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
Threat & Defense at a Glance
Threat & Defense Details
Likely Mitigating ControlsAI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Directly limits uncontrolled resource consumption that leads to denial-of-service.
Limiting concurrent sessions directly prevents uncontrolled resource consumption by capping the number of active sessions per user or account.
Analysis identifies uncontrolled resource consumption indicative of denial-of-service or abuse attempts.
Contingency plan testing includes resource exhaustion scenarios to verify recovery, making it harder for attackers to sustain exploits that cause uncontrolled consumption.
Updated contingency plans include current procedures to detect, contain, and recover from resource exhaustion, limiting an attacker's ability to sustain impact from uncontrolled consumption.
Alternate site allows resumption of operations if resource exhaustion at the primary site is exploited to cause unavailability.
Alternate telecommunications services enable resumption of essential functions when primary services become unavailable due to uncontrolled resource consumption.
The team can analyze and respond to resource exhaustion incidents, reducing the impact of attacks that exploit uncontrolled consumption weaknesses.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The vulnerability is a decompression limit bypass in a public HTTP library that enables an unauthenticated network attacker to trigger CPU/memory exhaustion (DoS) via a crafted small gzip payload; this directly matches application/system exploitation resulting in endpoint denial of service.
NVD Description
cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.35.0, cpp-httplib (httplib.h) does not enforce Server::set_payload_max_length() on the decompressed request body when using HandlerWithContentReader (streaming ContentReader) with Content-Encoding: gzip (or other supported encodings). A small compressed payload…
more
can expand beyond the configured payload limit and be processed by the application, enabling a payload size limit bypass and potential denial of service (CPU/memory exhaustion). This vulnerability is fixed in 0.35.0.
Deeper analysisAI
CVE-2026-28435 affects cpp-httplib, a C++11 single-file header-only cross-platform HTTP/HTTPS library, in versions prior to 0.35.0. The vulnerability arises because the library does not enforce the Server::set_payload_max_length() limit on the decompressed request body when using HandlerWithContentReader (streaming ContentReader) with Content-Encoding: gzip or other supported encodings. This allows a small compressed payload to expand beyond the configured payload limit and be processed by the application, resulting in a payload size limit bypass.
The vulnerability has a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), indicating it is exploitable over the network with low complexity, no privileges or user interaction required. An unauthenticated attacker can send a malicious HTTP request with a small gzip-compressed body that decompresses to a much larger size, causing the application to process excessive data and leading to denial of service through CPU or memory exhaustion.
The issue is fixed in cpp-httplib version 0.35.0. The GitHub security advisory (GHSA-xvfx-w463-6fpp) and the fixing commit (c99d7472b5cf4869d3897b9afc9792063a3d15a8) detail the patch, which enforces the payload length limit on decompressed content. Practitioners should upgrade to 0.35.0 or later to mitigate the vulnerability.
Details
- CWE(s)