Cyber Resilience

CVE-2025-63649

Memory Safety in Monkey-Project Monkey ≤ 1.8.5

Public PoCMemory Safety
Published
29 January 2026
Modified
19 February 2026
CVSS Score v3.1 7.5
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS Score 0.0095 59th percentile
Risk Priority 59 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2025-63649 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 Exploitation for Privilege Escalation (T1068); ranked in the top 41% 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 map to SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2025-63649 is an out-of-bounds read vulnerability in the http_parser_transfer_encoding_chunked function located in mk_server/mk_http_parser.c of the Monkey HTTP server at commit f37e984. This flaw affects deployments of Monkey, a lightweight open-source web server, where the parser mishandles chunked transfer encoding in HTTP requests, leading to potential memory access errors.

Remote attackers can exploit this vulnerability without authentication by sending a specially crafted POST request to a vulnerable Monkey server instance. The CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) indicates high severity due to its network accessibility, low attack complexity, and ability to cause a full Denial of Service (DoS) by crashing the server process, rendering the service unavailable.

Mitigation details and patches are documented in related advisories, including the Archer Security advisory at https://github.com/archersec/security-advisories/blob/master/monkey/monkey-advisory-2025.md and the Monkey project issue tracker at https://github.com/monkey/monkey/issues/426, which security practitioners should consult for upgrade instructions or workarounds. The vulnerability is associated with CWE-125 (Out-of-bounds Read).

EU & UK References

Vulnerability Data

An out-of-bounds read in the http_parser_transfer_encoding_chunked function (mk_server/mk_http_parser.c) of monkey commit f37e984 allows attackers to cause a Denial of Service (DoS) via sending a crafted POST request to the server.

CWE(s)
CWE-125

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
T1211 Exploitation for Stealth Stealth
Adversaries may exploit vulnerabilities to evade detection by hiding activity, suppressing logging, or operating within trusted or unmonitored components.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-63656Same product: Monkey-Project Monkey
CVE-2025-63657Same product: Monkey-Project Monkey
CVE-2025-63650Same product: Monkey-Project Monkey
CVE-2025-63653Same product: Monkey-Project Monkey
CVE-2025-63652Same product: Monkey-Project Monkey
CVE-2025-63651Same product: Monkey-Project Monkey
CVE-2025-63658Same product: Monkey-Project Monkey
CVE-2025-63655Same product: Monkey-Project Monkey
CVE-2026-64833Shared CWE-125
CVE-2024-38572Shared CWE-125

Affected Assets

monkey-project
monkey
≤ 1.8.5

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation directly finds out-of-bounds read flaws through static analysis, fuzzing, and dynamic bounds checks.

SA-8 Security and Privacy Engineering Principles partial match

Secure engineering principles require bounds checking and memory-safe constructs that stop out-of-bounds reads from being introduced.

SC-39 Process Isolation partial match

Process isolation confines the effects of an out-of-bounds read to the compromised process.

SI-10 Information Input Validation partial match

Input validation rejects malformed indices or lengths that would otherwise cause reads outside buffer bounds.

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.

PR.PS-06 mostly match
prevents

Secure-development practices such as bounds checking and memory-safe languages directly prevent out-of-bounds reads.

ID.RA-01 partial match
prevents

Vulnerability scanning and recording can discover instances of out-of-bounds reads after code is deployed.

PR.PS-02 partial match
prevents

Routine patching replaces vulnerable code containing out-of-bounds read flaws.

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.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development and acceptance includes fuzzing and static analysis that detect out-of-bounds read defects before release.

A.8.15 Logging partial match
finds

Logging can record evidence of an out-of-bounds read but does not prevent the weakness itself.

A.8.25 Secure development life cycle partial match
prevents

Secure development life cycle mandates input validation and bounds checking that directly prevent out-of-bounds reads.

A.8.26 Application security requirements partial match
prevents

Application security requirements include explicit bounds and memory-safety specifications that mitigate buffer over-reads.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure system architecture and engineering principles require memory-safe design patterns and runtime protections against out-of-bounds access.

A.8.28 Secure coding partial match
prevents

Secure coding standards explicitly forbid unsafe pointer arithmetic and mandate bounds-checked reads, eliminating CWE-125.

References