CVE-2025-63657
Published: 29 January 2026
Summary
CVE-2025-63657 is a high-severity Out-of-bounds Read (CWE-125) vulnerability in Monkey-Project Monkey. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 23.2% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 SC-5 (Denial-of-service Protection) and SI-10 (Information Input Validation).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
SI-2 requires timely flaw remediation, directly addressing this CVE by applying patches documented in the Monkey GitHub issue and Archer Security advisory to fix the out-of-bounds read.
SI-10 mandates input validation for HTTP requests, preventing crafted MIME type inputs from triggering the out-of-bounds read in mk_mimetype_find.
SC-5 provides denial-of-service protection mechanisms to limit the impact of application crashes caused by the out-of-bounds read vulnerability.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
OOB read in public-facing Monkey web server directly enables remote unauthenticated DoS via crafted HTTP request (T1190 for initial exploitation of public app; T1499.004 for resulting application crash via exploitation).
NVD Description
An out-of-bounds read in the mk_mimetype_find function (mk_server/mk_mimetype.c) of monkey commit f37e984 allows attackers to cause a Denial of Service (DoS) via sending a crafted HTTP request to the server.
Deeper analysisAI
CVE-2025-63657 is an out-of-bounds read vulnerability (CWE-125) in the mk_mimetype_find function within mk_server/mk_mimetype.c of the Monkey web server at commit f37e984. Published on 2026-01-29, this flaw affects instances of Monkey running the specified code version, enabling attackers to trigger a denial of service through malformed inputs.
Remote attackers can exploit this vulnerability over the network with low complexity and no authentication or user interaction required, as reflected in its CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). By sending a crafted HTTP request to the server, an attacker causes an out-of-bounds read, resulting in application crashes and temporary denial of service without impacting confidentiality or integrity.
Mitigation details and patches are documented in advisories including the Archer Security advisory at https://github.com/archersec/security-advisories/blob/master/monkey/monkey-advisory-2025.md and Monkey GitHub issue #426 at https://github.com/monkey/monkey/issues/426. Security practitioners should consult these resources for upgrade guidance or workarounds.
Details
- CWE(s)