Mongoose: Improper Resource Shutdown or Release
CVE-2026-6985 is a high-severity improper resource shutdown or release vulnerability in Mongoose from Cesanta, 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 Mongoose versions: 7.0; 7.1; 7.2, and others listed below. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.56% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of Mongoose you run against the affected versions below, and install the vendor's latest release.
- 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 |
|---|---|---|---|
| Cesanta | Mongoose | 7.0; 7.1; 7.2; 7.3; 7.4; 7.5; 7.6; 7.7; and 13 more ranges | Not stated |
Version data comes from the organisation that assigned the CVE. 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 NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 5.5 | Medium | CNA (vuldb.com) |
| CVSS 3.1 | 5.3 | Medium | CNA (vuldb.com) |
| CVSS 3.1 | 7.5 | High | NVD |
| CVSS 2.0 | 5.0 | Medium | CNA (vuldb.com) |
Official description
A weakness has been identified in Cesanta Mongoose up to 7.20. This vulnerability affects the function handle_opt of the file /src/net_builtin.c of the component TCP Option Handler. This manipulation of the argument optlen causes infinite loop. The attack is possible to be carried out remotely. The exploit has been made available to the public and could be used for attacks. Upgrading to version 7.21 is able to resolve this issue. Upgrading the affected component is advised. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Resource Shutdown or Release
The product does not release or incorrectly releases a resource before it is made available for re-use.
How developers prevent this class of flaw
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, languages such as Java, Ruby, and Lisp perform automatic garbage collection that releases memory for objects that have been deallocated.
- It is good practice to be responsible for freeing all resources you allocate and to be consistent with how and where you free memory in a function. If you allocate memory that you intend to free upon completion of the function, you must be sure to free the memory at all exit points for that function including error conditions.
- Memory should be allocated/freed using matching functions such as malloc/free, new/delete, and new[]/delete[].
More Improper Resource Shutdown or Release vulnerabilities (CWE-404)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- github.com/cesanta/mongoose/releases/tag/7.21Product, Release Notes
Third-party and government advisories
- vuldb.com/submit/796230Third Party Advisory, VDB Entry
- vuldb.com/vuln/359528Third Party Advisory, VDB Entry
Technical write-ups (may include proof of concept)
- github.com/dwBruijn/CVEs/blob/main/Mongoose/TCP_opt_dos.mdExploit, Third Party Advisory
Other references
- vuldb.com/vuln/359528/ctiPermissions Required, VDB Entry
Other vulnerabilities in Mongoose
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 8.8 High severity
- 9.1 Critical severity
- 9.1 Critical severity
Recent Improper Resource Shutdown or Release vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 8.1 High severity
- 7.5 High severity
- 7.5 High severity
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