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CVE-2019-1686

HIGHCVSS 8.6/10EPSS 1.59%

Last modified

CVE-2019-1686 is a high-severity vulnerability rated 8.6/10 on the CVSS scale. A vulnerability in the TCP flags inspection feature for access control lists (ACLs) on Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to bypass protection offered by a configured ACL on an affected device. The vulnerability is due to incorrect processing of the ACL applied to an interface of an affected device when Cisco Express Forwarding load balancing using the 3-tuple hash algorithm is enabled. EPSS estimates a 1.59% chance of exploitation in the next 30 days.

Description

A vulnerability in the TCP flags inspection feature for access control lists (ACLs) on Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to bypass protection offered by a configured ACL on an affected device. The vulnerability is due to incorrect processing of the ACL applied to an interface of an affected device when Cisco Express Forwarding load balancing using the 3-tuple hash algorithm is enabled. An attacker could exploit this vulnerability by sending traffic through an affected device that should otherwise be denied by the configured ACL. An exploit could allow the attacker to bypass protection offered by a configured ACL on the affected device. There are workarounds that address this vulnerability. Affected Cisco IOS XR versions are: Cisco IOS XR Software Release 5.1.1 and later till first fixed. First Fixed Releases: 6.5.2 and later, 6.6.1 and later.

Metrics

CVSS 3.1
8.6/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N

EPSS Probability
1.59%

72.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
CiscoIos Xr>= 5.1.1, < 6.5.2
CiscoIos Xr>= 6.5.3, < 6.6.1

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is CVE-2019-1686?
A vulnerability in the TCP flags inspection feature for access control lists (ACLs) on Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to bypass protection offered by a configured ACL on an affected device. The vulnerability is due to incorrect processing of the ACL applied to an interface of an affected device when Cisco Express Forwarding load balancing using the 3-tuple hash algorithm is enabled. An attacker could exploit this vulnerability by sending traffic through an affected device that should otherwise be denied by the configured ACL. An exploit could allow the attacker to bypass protection offered by a configured ACL on the affected device. There are workarounds that address this vulnerability. Affected Cisco IOS XR versions are: Cisco IOS XR Software Release 5.1.1 and later till first fixed. First Fixed Releases: 6.5.2 and later, 6.6.1 and later.
How severe is CVE-2019-1686?
CVE-2019-1686 has a CVSS score of 8.6/10 (HIGH severity). The EPSS model estimates a 1.59% probability of exploitation in the next 30 days.
How do I fix CVE-2019-1686?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST