# What is CVE-2019-11479?

> CVE-2019-11479 is a high-severity flaw (CVSS 7.5) in Linux kernel, published on 19 June 2019. 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 92%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2019-11479

## 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:** 68 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes.
- **Severity:** High (CVSS 7.5 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:** 92% (latest exploit-likelihood forecast)
- **Published:** 19 June 2019
- **Record last updated:** 7 November 2023
- **Main product:** Linux kernel
- **Affected products:** 21

## What is CVE-2019-11479? 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 take it offline.

### The official description

Jonathan Looney discovered that the Linux kernel default MSS is hard-coded to 48 bytes. This allows a remote peer to fragment TCP resend queues significantly more than if a larger MSS were enforced. A remote attacker could use this to cause a denial of service. This has been fixed in stable kernel releases 4.4.182, 4.9.182, 4.14.127, 4.19.52, 5.1.11, and is fixed in commits 967c05aee439e6e5d7d805e195b3a20ef5c433d6 and 5f3e2bf008c2221478101ee72f5cb4654b9fc363.

### What kind of flaw is it?

- CWE-405: Asymmetric Resource Consumption (Amplification)
- CWE-770: Allocation of Resources Without Limits or Throttling

### 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: No, nobody has to do anything
- What an attacker gets: Can take it offline

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

## Is CVE-2019-11479 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 92%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 92%, 92%, 92%, 92%, 92%, 92%, 92%.

### Timeline

- 19 June 2019: Published
- 7 November 2023: Record last updated
- 19 November 2025: Exploit likelihood jumped
- 22 November 2025: Exploit likelihood fell

### How Precursor Intelligence ranks it

CVE-2019-11479 scores **68 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-2019-11479?

The published record lists 21 products. Versions are as published: "4.4 to before 4.4.182" means from 4.4 up to, but not including, 4.4.182.

- [Linux kernel](https://www.precursorintelligence.com/product/linux/linux_kernel) by [Linux](https://www.precursorintelligence.com/vendors/linux) (Operating system): 4.4 to before 4.4.182, 4.9 to before 4.9.182, 4.14 to before 4.14.127, 4.19 to before 4.19.52, 5.1 to before 5.1.11
- [Big-IP Access Policy Manager](https://www.precursorintelligence.com/product/f5/big-ip_access_policy_manager) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 11.5.2 to before 11.6.5.1, 12.1.0 to before 12.1.5.1, 13.1.0 to before 13.1.3.2, 14.0.0 to before 14.0.1.1, 14.1.2 to before 14.1.2.1, 15.0.0 to before 15.0.1.1
- [Big-IP Advanced Firewall Manager](https://www.precursorintelligence.com/product/f5/big-ip_advanced_firewall_manager) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 11.5.2 to before 11.6.5.1, 12.1.0 to before 12.1.5.1, 13.1.0 to before 13.1.3.2, 14.0.0 to before 14.0.1.1, 14.1.2 to before 14.1.2.1, 15.0.0 to before 15.0.1.1
- [Big-IP Analytics](https://www.precursorintelligence.com/product/f5/big-ip_analytics) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 11.5.2 to before 11.6.5.1, 12.1.0 to before 12.1.5.1, 13.1.0 to before 13.1.3.2, 14.0.0 to before 14.0.1.1, 14.1.2 to before 14.1.2.1, 15.0.0 to before 15.0.1.1
- [Big-IP Application Acceleration Manager](https://www.precursorintelligence.com/product/f5/big-ip_application_acceleration_manager) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 11.5.2 to before 11.6.5.1, 12.1.0 to before 12.1.5.1, 13.1.0 to before 13.1.3.2, 14.0.0 to before 14.0.1.1, 14.1.2 to before 14.1.2.1, 15.0.0 to before 15.0.1.1
- [Big-IP Application Security Manager](https://www.precursorintelligence.com/product/f5/big-ip_application_security_manager) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 11.5.2 to before 11.6.5.1, 12.1.0 to before 12.1.5.1, 13.1.0 to before 13.1.3.2, 14.0.0 to before 14.0.1.1, 14.1.2 to before 14.1.2.1, 15.0.0 to before 15.0.1.1
- [Big-IP Domain Name System](https://www.precursorintelligence.com/product/f5/big-ip_domain_name_system) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 11.5.2 to before 11.6.5.1, 12.1.0 to before 12.1.5.1, 13.1.0 to before 13.1.3.2, 14.0.0 to before 14.0.1.1, 14.1.2 to before 14.1.2.1, 15.0.0 to before 15.0.1.1
- [Big-IP Edge Gateway](https://www.precursorintelligence.com/product/f5/big-ip_edge_gateway) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 11.5.2 to before 11.6.5.1, 12.1.0 to before 12.1.5.1, 13.1.0 to before 13.1.3.2, 14.0.0 to before 14.0.1.1, 14.1.2 to before 14.1.2.1, 15.0.0 to before 15.0.1.1
- [Big-IP Fraud Protection Service](https://www.precursorintelligence.com/product/f5/big-ip_fraud_protection_service) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 11.5.2 to before 11.6.5.1, 12.1.0 to before 12.1.5.1, 13.1.0 to before 13.1.3.2, 14.0.0 to before 14.0.1.1, 14.1.2 to before 14.1.2.1, 15.0.0 to before 15.0.1.1
- [Big-IP Global Traffic Manager](https://www.precursorintelligence.com/product/f5/big-ip_global_traffic_manager) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 11.5.2 to before 11.6.5.1, 12.1.0 to before 12.1.5.1, 13.1.0 to before 13.1.3.2, 14.0.0 to before 14.0.1.1, 14.1.2 to before 14.1.2.1, 15.0.0 to before 15.0.1.1
- [Big-IP Link Controller](https://www.precursorintelligence.com/product/f5/big-ip_link_controller) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 11.5.2 to before 11.6.5.1, 12.1.0 to before 12.1.5.1, 13.1.0 to before 13.1.3.2, 14.0.0 to before 14.0.1.1, 14.1.2 to before 14.1.2.1, 15.0.0 to before 15.0.1.1
- [Big-IP Local Traffic Manager](https://www.precursorintelligence.com/product/f5/big-ip_local_traffic_manager) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 11.5.2 to before 11.6.5.1, 12.1.0 to before 12.1.5.1, 13.1.0 to before 13.1.3.2, 14.0.0 to before 14.0.1.1, 14.1.2 to before 14.1.2.1, 15.0.0 to before 15.0.1.1
- [Big-IP Policy Enforcement Manager](https://www.precursorintelligence.com/product/f5/big-ip_policy_enforcement_manager) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 11.5.2 to before 11.6.5.1, 12.1.0 to before 12.1.5.1, 13.1.0 to before 13.1.3.2, 14.0.0 to before 14.0.1.1, 14.1.2 to before 14.1.2.1, 15.0.0 to before 15.0.1.1
- [Big-IP Webaccelerator](https://www.precursorintelligence.com/product/f5/big-ip_webaccelerator) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 11.5.2 to before 11.6.5.1, 12.1.0 to before 12.1.5.1, 13.1.0 to before 13.1.3.2, 14.0.0 to before 14.0.1.1, 14.1.2 to before 14.1.2.1, 15.0.0 to before 15.0.1.1
- [Ubuntu Linux](https://www.precursorintelligence.com/product/canonical/ubuntu_linux) by [Canonical](https://www.precursorintelligence.com/vendors/canonical) (Operating system): 14.04, 16.04, 18.04, 18.10, 19.04
- [Big-Iq Centralized Management](https://www.precursorintelligence.com/product/f5/big-iq_centralized_management) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 5.1.0 to 5.4.0, 6.0.0 to 6.1.0
- [Enterprise Linux](https://www.precursorintelligence.com/product/redhat/enterprise_linux) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 7.0
- [Enterprise Manager](https://www.precursorintelligence.com/product/f5/enterprise_manager) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 3.1.1
- [Iworkflow](https://www.precursorintelligence.com/product/f5/iworkflow) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 2.3.0
- [Traffix Signaling Delivery Controller](https://www.precursorintelligence.com/product/f5/traffix_signaling_delivery_controller) by [F5](https://www.precursorintelligence.com/vendors/f5) (Application): 5.0.0 to 5.1.0
- [Virtualization Host](https://www.precursorintelligence.com/product/redhat/virtualization_host) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 4.0

## How do I fix CVE-2019-11479?

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

- [git.kernel.org](https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/commit/?id=5f3e2bf008c2221478101ee72f5cb4654b9fc363) (Mailing list, Patch, Vendor advisory)
- [git.kernel.org](https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/commit/?id=967c05aee439e6e5d7d805e195b3a20ef5c433d6) (Mailing list, Patch, Vendor advisory)
- [github.com](https://github.com/Netflix/security-bulletins/blob/master/advisories/third-party/2019-001.md) (Patch, Third-party advisory)
- [wiki.ubuntu.com](https://wiki.ubuntu.com/SecurityTeam/KnowledgeBase/SACKPanic) (Mitigation, Third-party advisory)
- [arubanetworks.com](http://www.arubanetworks.com/assets/alert/ARUBA-PSA-2020-010.txt) (Third-party advisory)
- [openwall.com](http://www.openwall.com/lists/oss-security/2019/06/28/2) (Mailing list, Third-party advisory)
- [openwall.com](http://www.openwall.com/lists/oss-security/2019/07/06/3) (Mailing list, Third-party advisory)
- [openwall.com](http://www.openwall.com/lists/oss-security/2019/07/06/4) (Mailing list, Third-party advisory)
- [securityfocus.com](http://www.securityfocus.com/bid/108818) (Third-party advisory, Vulnerability database)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2019:1594) (Third-party advisory)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2019:1602) (Third-party advisory)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2019:1699) (Third-party advisory)
- [access.redhat.com](https://access.redhat.com/security/vulnerabilities/tcpsack) (Third-party advisory)
- [cert-portal.siemens.com](https://cert-portal.siemens.com/productcert/pdf/ssa-462066.pdf) (Third-party advisory)
- [kb.pulsesecure.net](https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44193) (Third-party advisory)
- [kc.mcafee.com](https://kc.mcafee.com/corporate/index?page=content&id=SB10287) (Third-party advisory)
- [psirt.global.sonicwall.com](https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2019-0008) (Third-party advisory)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20190625-0001/) (Third-party advisory)
- [support.f5.com](https://support.f5.com/csp/article/K35421172) (Third-party advisory)
- [support.f5.com](https://support.f5.com/csp/article/K35421172?utm_source=f5support&amp%3Butm_medium=RSS)
- [usn.ubuntu.com](https://usn.ubuntu.com/4041-1/) (Third-party advisory)
- [usn.ubuntu.com](https://usn.ubuntu.com/4041-2/) (Third-party advisory)
- [kb.cert.org](https://www.kb.cert.org/vuls/id/905115) (Third-party advisory, Government resource)
- [oracle.com](https://www.oracle.com/security-alerts/cpujan2020.html) (Third-party advisory)
- [oracle.com](https://www.oracle.com/security-alerts/cpuoct2020.html)
- [synology.com](https://www.synology.com/security/advisory/Synology_SA_19_28) (Third-party advisory)
- [us-cert.gov](https://www.us-cert.gov/ics/advisories/icsa-19-253-03) (Third-party advisory, Government resource)
- [us-cert.gov](https://www.us-cert.gov/ics/advisories/icsma-20-170-06) (Third-party advisory, Government resource)

## Questions

### What is CVE-2019-11479?

CVE-2019-11479 is a high-severity flaw in Linux kernel, published on 19 June 2019. It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can take it offline.

### How serious is CVE-2019-11479?

It scores 7.5 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2019-11479 is 68 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-2019-11479 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 92%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2019-11479 affect?

For Linux kernel: 4.4 to before 4.4.182, 4.9 to before 4.9.182, 4.14 to before 4.14.127, 4.19 to before 4.19.52, 5.1 to before 5.1.11. The record lists 21 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2019-11479?

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-2019-11479 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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