Varnich Cache: Inconsistent Interpretation of HTTP Requests
CVE-2022-23959 is a critical-severity inconsistent interpretation of HTTP requests vulnerability in Varnich Cache from Varnish-software, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 6.6.2, 4.1.11r6 as the first without the flaw, so updating Varnich Cache to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 2.01% chance of exploitation within 30 days, higher than 81% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Varnich Cache to 6.6.2 or 4.1.11r6, whichever matches your release line, or a later version.
- Update Varnish Cache to 6.0.10 or a later version.
- Update Varnish Cache Plus to 6.0.9r4 or a later version.
- Read the advisory on docs.varnish-software.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 |
|---|---|---|---|
| Varnish-software | Varnich Cache | 1.0.0 up to, but not including, 6.6.2; 4.1.1 up to, but not including, 4.1.11r6; 4.1 | 6.6.2, 4.1.11r6 |
| Varnish-software | Varnish Cache | 6.0.0 up to, but not including, 6.0.10 | 6.0.10 |
| Varnish-software | Varnish Cache Plus | 6.0.0 up to, but not including, 6.0.9r4 | 6.0.9r4 |
| Fedora Project | Fedora | 35 | Not stated |
| Debian | Debian Linux | 9.0; 10.0; 11.0 | Not stated |
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
- 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
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.1 | Critical | NVD |
| CVSS 2.0 | 6.4 | Medium | NVD |
Official description
In Varnish Cache before 6.6.2 and 7.x before 7.0.2, Varnish Cache 6.0 LTS before 6.0.10, and and Varnish Enterprise (Cache Plus) 4.1.x before 4.1.11r6 and 6.0.x before 6.0.9r4, request smuggling can occur for HTTP/1 connections.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Inconsistent Interpretation of HTTP Requests
The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.
How developers prevent this class of flaw
- Use a web server that employs a strict HTTP parsing procedure, such as Apache.
- Terminate the client session after each request.
More Inconsistent Interpretation of HTTP Requests vulnerabilities (CWE-444)
Timeline
- CVE record published.
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
- lists.debian.org/debian-lts-announce/2022/02/msg00014.htmlMailing List, Third Party Advisory
- debian.org/security/2022/dsa-5088Third Party Advisory
Other references
Recent Inconsistent Interpretation of HTTP Requests vulnerabilities
- 7.4 High severity
- 7.5 High severity
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