picotls: Double Free
CVE-2024-45402 is a critical-severity double free vulnerability in picotls from H2o, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected picotls versions: < 9b88159ce763d680e4a13b6e8f3171ae923a535d. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.48% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update picotls to 9b88159ce763d680e4a13b6e8f3171ae923a535d or a later version.
- 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 |
|---|---|---|---|
| H2o | picotls | < 9b88159ce763d680e4a13b6e8f3171ae923a535d | Not stated |
| H2o Project | picotls | before 9b88159ce763d680e4a13b6e8f3171ae923a535d | 9b88159ce763d680e4a13b6e8f3171ae923a535d |
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
- 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:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.6 | High | CNA (github.com) |
| CVSS 3.1 | 9.8 | Critical | NVD |
Official description
Picotls is a TLS protocol library that allows users select different crypto backends based on their use case. When parsing a spoofed TLS handshake message, picotls (specifically, bindings within picotls that call the crypto libraries) may attempt to free the same memory twice. This double free occurs during the disposal of multiple objects without any intervening calls to malloc Typically, this triggers the malloc implementation to detect the error and abort the process. However, depending on the internals of malloc and the crypto backend being used, the flaw could potentially lead to a use-after-free scenario, which might allow for arbitrary code execution. The vulnerability is addressed with commit 9b88159ce763d680e4a13b6e8f3171ae923a535d.
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: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Double Free vulnerabilities
- 7.5 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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