cfnts: Out-of-bounds Read
CVE-2023-3036 is a high-severity out-of-bounds read vulnerability in cfnts from Cloudflare, 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. The record lists version < 783490b as the first without the flaw, so updating cfnts to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 2.24% chance of exploitation within 30 days, higher than 83% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update cfnts to < 783490b 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 |
|---|---|---|---|
| Cloudflare | cfnts | before < 783490b | < 783490b |
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 3.1 | 8.6 | High | CNA (cloudflare.com) |
| CVSS 3.1 | 7.5 | High | NVD |
Official description
An unchecked read in NTP server in github.com/cloudflare/cfnts prior to commit 783490b https://github.com/cloudflare/cfnts/commit/783490b913f05e508a492cd7b02e3c4ec2297b71 enabled a remote attacker to trigger a panic by sending an NTSAuthenticator packet with extension length longer than the packet contents.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Read
The product reads data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that provides appropriate memory abstractions.
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/cloudflare/cfnts/security/advisories/GHSA-pwx6-gw47-96cpThird Party Advisory
Recent Out-of-bounds Read vulnerabilities
- 9.1 Critical severity
- 7.5 High severity
- 7.8 High severity
- 7.8 High severity
- 7.5 High severity
- 8.1 High severity
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