# What is CVE-2021-43797?

> CVE-2021-43797 is a medium-severity flaw (CVSS 6.5) in Netty, published on 9 December 2021. It is not on the list of flaws known to be exploited today. The latest forecast puts its chance of use in the next 30 days at 2.9%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2021-43797

## At a glance

- **Verdict:** Plan it in. No sign of exploitation and a low forecast. Patch it in your normal update cycle.
- **Precursor Intelligence risk score:** 37 out of 100 (Low); action: Monitor. Kept up to date as the evidence changes.
- **Severity:** Medium (CVSS 6.5 out of 10)
- **Known to be exploited:** No, not on the list of flaws known to be exploited today
- **Chance of use in the next 30 days:** 2.9% (latest exploit-likelihood forecast)
- **Published:** 9 December 2021
- **Record last updated:** 24 February 2023
- **Main product:** Netty
- **Affected products:** 18

## What is CVE-2021-43797? In plain terms

It can be attacked from anywhere on the internet without logging in, but a person has to take an action first. If it works, the attacker can change data.

### The official description

Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. Netty prior to version 4.1.71.Final skips control chars when they are present at the beginning / end of the header name. It should instead fail fast as these are not allowed by the spec and could lead to HTTP request smuggling. Failing to do the validation might cause netty to "sanitize" header names before it forward these to another remote system when used as proxy. This remote system can't see the invalid usage anymore, and therefore does not do the validation itself. Users should upgrade to version 4.1.71.Final.

### What kind of flaw is it?

- CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

### How an attack on it works

- Where an attacker can be: Anywhere on the internet
- How hard it is to pull off: Easy: no special conditions
- Login needed first: No login needed
- Does someone have to click: Yes, a person has to take an action
- What an attacker gets: Can change data

Severity vector: `CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N`

## Is CVE-2021-43797 being exploited? Not that we know of

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 2.9%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 2.9%, 2.9%, 2.9%, 2.9%, 2.9%, 2.9%, 2.9%.

### Timeline

- 9 December 2021: Published
- 24 February 2023: Record last updated

### How Precursor Intelligence ranks it

CVE-2021-43797 scores **37 out of 100 (Low)**, with the action "Monitor".

Every published flaw gets a risk score from 0 to 100, kept up to date as the evidence changes. Four things go into the score, from the one that counts most to the ones that count less:

- Evidence it is being exploited: biggest factor
- How severe it is: strong factor
- How widely exposed it is: smaller factor
- Threat activity around it: smaller factor

85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score. When this flaw matches software you track, it lands in your list with its score and the reasons behind it.

## Who is affected by CVE-2021-43797?

The published record lists 18 products. Versions are as published: "before 4.1.71" means every version up to, but not including, 4.1.71.

- [Netty](https://www.precursorintelligence.com/product/netty/netty) by [Netty](https://www.precursorintelligence.com/vendors/netty) (Application): before 4.1.71
- [Coherence](https://www.precursorintelligence.com/product/oracle/coherence) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 12.2.1.4.0, 14.1.1.0.0
- [Debian Linux](https://www.precursorintelligence.com/product/debian/debian_linux) by [Debian](https://www.precursorintelligence.com/vendors/debian) (Operating system): 10.0, 11.0
- [Helidon](https://www.precursorintelligence.com/product/oracle/helidon) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 1.4.10, 2.4.0
- [Peoplesoft Enterprise Peopletools](https://www.precursorintelligence.com/product/oracle/peoplesoft_enterprise_peopletools) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 8.58, 8.59
- [Banking Deposits and Lines of Credit Servicing](https://www.precursorintelligence.com/product/oracle/banking_deposits_and_lines_of_credit_servicing) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 2.7
- [Banking Party Management](https://www.precursorintelligence.com/product/oracle/banking_party_management) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 2.7.0
- [Banking Platform](https://www.precursorintelligence.com/product/oracle/banking_platform) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 2.6.2
- [Communications Cloud Native Core Binding Support Function](https://www.precursorintelligence.com/product/oracle/communications_cloud_native_core_binding_support_function) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 1.11.0
- [Communications Cloud Native Core Network Slice Selection Function](https://www.precursorintelligence.com/product/oracle/communications_cloud_native_core_network_slice_selection_function) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 1.8.0
- [Communications Cloud Native Core Policy](https://www.precursorintelligence.com/product/oracle/communications_cloud_native_core_policy) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 1.15.0
- [Communications Cloud Native Core Security Edge Protection Proxy](https://www.precursorintelligence.com/product/oracle/communications_cloud_native_core_security_edge_protection_proxy) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 1.7.0
- [Communications Cloud Native Core Unified Data Repository](https://www.precursorintelligence.com/product/oracle/communications_cloud_native_core_unified_data_repository) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 1.15.0
- [Communications Design Studio](https://www.precursorintelligence.com/product/oracle/communications_design_studio) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 7.4.2
- [Communications Instant Messaging Server](https://www.precursorintelligence.com/product/oracle/communications_instant_messaging_server) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 8.1
- [Oncommand Workflow Automation](https://www.precursorintelligence.com/product/netapp/oncommand_workflow_automation) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Quarkus](https://www.precursorintelligence.com/product/quarkus/quarkus) by [Quarkus](https://www.precursorintelligence.com/vendors/quarkus) (Application): before 2.5.3
- [Snapcenter](https://www.precursorintelligence.com/product/netapp/snapcenter) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified

## How do I fix CVE-2021-43797?

1. **Check whether you run it.** Compare your versions with the affected products above. Not sure what you run? Precursor Intelligence can work it out from your public website, or you can pick it from a list.
2. **Apply the vendor’s fix.** Install the update named in the vendor’s advisory. We’ve put the advisories and patch notes first in the list.
3. **If you can’t patch today.** Follow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in.
4. **Keep an eye on it.** Track the product and we tell you as soon as we spot this flaw on the list of exploited flaws, or a jump in its exploit likelihood.

### References

- [github.com](https://github.com/netty/netty/commit/07aa6b5938a8b6ed7a6586e066400e2643897323) (Patch, Third-party advisory)
- [oracle.com](https://www.oracle.com/security-alerts/cpuapr2022.html) (Patch, Third-party advisory)
- [oracle.com](https://www.oracle.com/security-alerts/cpujul2022.html) (Patch, Third-party advisory)
- [github.com](https://github.com/netty/netty/security/advisories/GHSA-wx5j-54mm-rqqq) (Third-party advisory)
- [lists.debian.org](https://lists.debian.org/debian-lts-announce/2023/01/msg00008.html) (Mailing list, Third-party advisory)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20220107-0003/) (Third-party advisory)
- [debian.org](https://www.debian.org/security/2023/dsa-5316) (Third-party advisory)

## Questions

### What is CVE-2021-43797?

CVE-2021-43797 is a medium-severity flaw in Netty, published on 9 December 2021. It can be attacked from anywhere on the internet without logging in, but a person has to take an action first. If it works, the attacker can change data.

### How serious is CVE-2021-43797?

It scores 6.5 out of 10 on the CVSS severity scale, which is medium. Our risk score for CVE-2021-43797 is 37 out of 100, which is Low. Its action is "Monitor". No sign of exploitation and a low forecast. Patch it in your normal update cycle.

### Is CVE-2021-43797 being exploited?

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 2.9%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2021-43797 affect?

For Netty: before 4.1.71. The record lists 18 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2021-43797?

Install the update the vendor names in its advisory, linked first under "How do I fix" on this page. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet.

## Does CVE-2021-43797 affect you?

Precursor Intelligence keeps checking for you:

- **Tell us what you run.** Pick your software from a list, or let us work it out from your website.
- **We match it to every flaw.** Over 400,000 published flaws, checked against your list.
- **Ranked by real-world risk.** Every flaw gets a 0 to 100 risk score, kept up to date, led by evidence criminals are using it.
- **Told as soon as we know.** An alert by email, in the app or by webhook to your own tools.

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