# What is CVE-2016-5388?

> CVE-2016-5388 is a high-severity flaw (CVSS 8.1) in Tomcat from Apache, published on 19 July 2016. 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 51%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2016-5388

## At a glance

- **Verdict:** Fix this soon. Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.
- **Precursor Intelligence risk score:** 48 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes.
- **Severity:** High (CVSS 8.1 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:** 51% (latest exploit-likelihood forecast)
- **Published:** 19 July 2016
- **Record last updated:** 12 April 2025
- **Main product:** Tomcat from Apache
- **Affected products:** 11

## What is CVE-2016-5388? In plain terms

It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can read data, change data and take it offline.

### The official description

Apache Tomcat 7.x through 7.0.70 and 8.x through 8.5.4, when the CGI Servlet is enabled, follows RFC 3875 section 4.1.18 and therefore does not protect applications from the presence of untrusted client data in the HTTP_PROXY environment variable, which might allow remote attackers to redirect an application's outbound HTTP traffic to an arbitrary proxy server via a crafted Proxy header in an HTTP request, aka an "httpoxy" issue. NOTE: the vendor states "A mitigation is planned for future releases of Tomcat, tracked as CVE-2016-5388"; in other words, this is not a CVE ID for a vulnerability.

### What kind of flaw is it?

- CWE-284: Improper Access Control

### How an attack on it works

- Where an attacker can be: Anywhere on the internet
- How hard it is to pull off: Hard: conditions must line up
- Login needed first: No login needed
- Does someone have to click: No, nobody has to do anything
- What an attacker gets: Can read data, change data and take it offline

Severity vector: `CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H`

## Is CVE-2016-5388 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 51%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 51%, 51%, 51%, 51%, 51%, 51%, 51%.

### Timeline

- 19 July 2016: Published
- 12 April 2025: Record last updated
- 2 July 2025: Exploit likelihood fell
- 5 July 2025: Exploit likelihood jumped

### How Precursor Intelligence ranks it

CVE-2016-5388 scores **48 out of 100 (Medium)**, with the action "Plan remediation".

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-2016-5388?

The published record lists 11 products.

- [Tomcat](https://www.precursorintelligence.com/product/apache/tomcat) by [Apache](https://www.precursorintelligence.com/vendors/apache) (Application): 6.0 to 6.0.45, 7.0 to 7.0.70, 8.0 to 8.5.4
- [Enterprise Linux Desktop](https://www.precursorintelligence.com/product/redhat/enterprise_linux_desktop) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 6.0, 7.0
- [Enterprise Linux Hpc Node](https://www.precursorintelligence.com/product/redhat/enterprise_linux_hpc_node) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 6.0, 7.0
- [Enterprise Linux Server](https://www.precursorintelligence.com/product/redhat/enterprise_linux_server) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 6.0, 7.0
- [Enterprise Linux Workstation](https://www.precursorintelligence.com/product/redhat/enterprise_linux_workstation) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 6.0, 7.0
- [Linux](https://www.precursorintelligence.com/product/oracle/linux) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Operating system): 6, 7
- [Enterprise Linux Hpc Node Eus](https://www.precursorintelligence.com/product/redhat/enterprise_linux_hpc_node_eus) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 7.2
- [Enterprise Linux Server Aus](https://www.precursorintelligence.com/product/redhat/enterprise_linux_server_aus) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 7.2
- [Enterprise Linux Server Eus](https://www.precursorintelligence.com/product/redhat/enterprise_linux_server_eus) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 7.2
- [Enterprise Linux Server Tus](https://www.precursorintelligence.com/product/redhat/enterprise_linux_server_tus) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 7.2
- [System Management Homepage](https://www.precursorintelligence.com/product/hp/system_management_homepage) by [HP](https://www.precursorintelligence.com/vendors/hp) (Application): up to 7.5.5.0

## How do I fix CVE-2016-5388?

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

- [oracle.com](http://www.oracle.com/technetwork/security-advisory/cpujul2017-3236622.html) (Patch, Third-party advisory)
- [securitytracker.com](http://www.securitytracker.com/id/1036331) (Third-party advisory, Vulnerability database, Vendor advisory)
- [tomcat.apache.org](https://tomcat.apache.org/tomcat-7.0-doc/changelog.html) (Release notes, Vendor advisory)
- [apache.org](https://www.apache.org/security/asf-httpoxy-response.txt) (Vendor advisory)
- [lists.opensuse.org](http://lists.opensuse.org/opensuse-updates/2016-09/msg00025.html) (Third-party advisory)
- [rhn.redhat.com](http://rhn.redhat.com/errata/RHSA-2016-1624.html) (Third-party advisory)
- [rhn.redhat.com](http://rhn.redhat.com/errata/RHSA-2016-2045.html) (Third-party advisory)
- [rhn.redhat.com](http://rhn.redhat.com/errata/RHSA-2016-2046.html) (Third-party advisory)
- [kb.cert.org](http://www.kb.cert.org/vuls/id/797896) (Third-party advisory, Government resource)
- [oracle.com](http://www.oracle.com/technetwork/topics/security/linuxbulletinoct2016-3090545.html) (Third-party advisory)
- [securityfocus.com](http://www.securityfocus.com/bid/91818) (Third-party advisory, Vulnerability database)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2016:1635) (Third-party advisory)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2016:1636) (Third-party advisory)
- [h20566.www2.hpe.com](https://h20566.www2.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbhf03770en_us) (Third-party advisory)
- [h20566.www2.hpe.com](https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05320149) (Third-party advisory)
- [h20566.www2.hpe.com](https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05324759) (Third-party advisory)
- [h20566.www2.hpe.com](https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05390722) (Third-party advisory)
- [httpoxy.org](https://httpoxy.org/) (Third-party advisory)
- [lists.apache.org](https://lists.apache.org/thread.html/053d9ce4d579b02203db18545fee5e33f35f2932885459b74d1e4272%40%3Cissues.activemq.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/6b414817c2b0bf351138911c8c922ec5dd577ebc0b9a7f42d705752d%40%3Cissues.activemq.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/6d3d34adcf3dfc48e36342aa1f18ce3c20bb8e4c458a97508d5bfed1%40%3Cissues.activemq.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r2853582063cfd9e7fbae1e029ae004e6a83482ae9b70a698996353dd%40%3Cusers.tomcat.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/rc6b2147532416cc736e68a32678d3947b7053c3085cf43a9874fd102%40%3Cusers.tomcat.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/rf21b368769ae70de4dee840a3228721ae442f1d51ad8742003aefe39%40%3Cusers.tomcat.apache.org%3E)
- [lists.debian.org](https://lists.debian.org/debian-lts-announce/2019/08/msg00015.html)

## Questions

### What is CVE-2016-5388?

CVE-2016-5388 is a high-severity flaw in Tomcat from Apache, published on 19 July 2016. It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can read data, change data and take it offline.

### How serious is CVE-2016-5388?

It scores 8.1 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2016-5388 is 48 out of 100, which is Medium. Its action is "Plan remediation". Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.

### Is CVE-2016-5388 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 51%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2016-5388 affect?

For Tomcat from Apache: 6.0 to 6.0.45, 7.0 to 7.0.70, 8.0 to 8.5.4. The record lists 11 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2016-5388?

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-2016-5388 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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