Monkey: NULL Pointer Dereference
CVE-2025-63655 is a high-severity NULL pointer dereference vulnerability in Monkey from Monkey-project, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Monkey versions: 1.8.5 and earlier. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 8.56% chance of exploitation within 30 days, which is in the top 4.85% of all scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of Monkey you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Monkey-project | Monkey | 1.8.5 and earlier | Not stated |
Version data comes from NVD's product matching. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CISA (ADP).
Official description
A NULL pointer dereference in the mk_http_range_parse function (mk_server/mk_http.c) of monkey commit f37e984 allows attackers to cause a Denial of Service (DoS) via sending a crafted HTTP request to the server.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: NULL Pointer Dereference
The product dereferences a pointer that it expects to be valid but is NULL.
How developers prevent this class of flaw
- For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
- Select a programming language that is not susceptible to these issues.
- Check the results of all functions that return a value and verify that the value is non-null before acting upon it.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
- github.com/archersec/security-advisories/blob/master/monkey/monkey-advisory-2025.mdExploit, Third Party Advisory
Technical write-ups (may include proof of concept)
- github.com/monkey/monkey/issues/427Exploit, Third Party Advisory
Other vulnerabilities in Monkey
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- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
Recent NULL Pointer Dereference vulnerabilities
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- 7.5 High severity
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- 7.5 High severity
- 7.4 High severity
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