Kerberos 5: Double Free
CVE-2023-39975 is a high-severity double free vulnerability in Kerberos 5 from Mit, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists version 1.21.2 as the first without the flaw, so updating Kerberos 5 to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 1.47% chance of exploitation within 30 days, higher than 74% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Kerberos 5 to 1.21.2 or a later version.
- Read the advisory on web.mit.edu for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Mit | Kerberos 5 | 1.21 up to, but not including, 1.21.2 | 1.21.2 |
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
- 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:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.8 | High | NVD |
| CVSS 3.1 | 8.8 | High | CISA (ADP) |
Official description
kdc/do_tgs_req.c in MIT Kerberos 5 (aka krb5) 1.21 before 1.21.2 has a double free that is reachable if an authenticated user can trigger an authorization-data handling failure. Incorrect data is copied from one ticket to another.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Double Free
The product calls free() twice on the same memory address.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- Ensure that each allocation is freed only once. After freeing a chunk, set the pointer to NULL to ensure the pointer cannot be freed again. In complicated error conditions, be sure that clean-up routines respect the state of allocation properly. If the language is object oriented, ensure that object destructors delete each chunk of memory only once.
- Use a static analysis tool to find double free instances.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Patches and release notes
Other references
Other vulnerabilities in Kerberos 5
- 7.5 High severity
- 7.5 High severity
- 7.1 High severity
- 9.1 Critical severity
- 7.5 High severity
- 8.8 High severity
Recent Double Free vulnerabilities
- 7.1 High severity
- 7.5 High severity
- 7.5 High severity
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
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