Kamailio: Use After Free
CVE-2025-12205 is a high-severity use after free vulnerability in Kamailio, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. Affected Kamailio versions: 5.5. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.23% 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 Kamailio you run against the affected versions below, and install the vendor's latest release.
Affected products and versions
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
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 1.9 | Low | CNA (vuldb.com) |
| CVSS 3.1 | 5.3 | Medium | CNA (vuldb.com) |
| CVSS 3.1 | 7.8 | High | NVD |
| CVSS 2.0 | 4.3 | Medium | CNA (vuldb.com) |
Official description
A vulnerability was detected in Kamailio 5.5. The affected element is the function sr_push_yy_state of the file src/core/cfg.lex of the component Configuration File Handler. The manipulation results in use after free. The attack must be initiated from a local position. The exploit is now public and may be used. The real existence of this vulnerability is still doubted at the moment. This attack requires manipulating config files which might not be a realistic scenario in many cases. The vendor was contacted early about this disclosure but did not respond in any way.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- vuldb.com/?id.329875Third Party Advisory, VDB Entry
- vuldb.com/?submit.673225Third Party Advisory, VDB Entry
Technical write-ups (may include proof of concept)
- shimo.im/docs/ZzkLMVMLOzIRlpAQ/Exploit, Third Party Advisory
Other references
- vuldb.com/?ctiid.329875Permissions Required, VDB Entry
- openwall.com/lists/oss-security/2025/11/02/3
- openwall.com/lists/oss-security/2025/10/27/12
- openwall.com/lists/oss-security/2025/10/27/8
- openwall.com/lists/oss-security/2025/10/27/8Issue Tracking, Mailing List
Other vulnerabilities in Kamailio
- 8.3 High severity
- 7.5 High severity
- 7.4 High severity
- 7.5 High severity
- 7.8 High severity
Recent Use After Free vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 8.8 High severity
- 8.8 High severity
- 7.5 High severity
- 7.8 High severity
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