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CVE-2023-4809

HIGHCVSS 7.5/10EPSS 0.68%

Last modified

CVE-2023-4809 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. In pf packet processing with a 'scrub fragment reassemble' rule, a packet containing multiple IPv6 fragment headers would be reassembled, and then immediately processed. That is, a packet with multiple fragment extension headers would not be recognized as the correct ultimate payload. EPSS estimates a 0.68% chance of exploitation in the next 30 days.

Description

In pf packet processing with a 'scrub fragment reassemble' rule, a packet containing multiple IPv6 fragment headers would be reassembled, and then immediately processed. That is, a packet with multiple fragment extension headers would not be recognized as the correct ultimate payload. Instead a packet with multiple IPv6 fragment headers would unexpectedly be interpreted as a fragmented packet, rather than as whatever the real payload is. As a result, IPv6 fragments may bypass pf firewall rules written on the assumption all fragments have been reassembled and, as a result, be forwarded or processed by the host.

Metrics

CVSS 3.1
7.5/10

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

EPSS Probability
0.68%

47.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
FreebsdFreebsd< 12.4
FreebsdFreebsd>= 13.0, < 13.2
FreebsdFreebsd12.4
FreebsdFreebsd13.2

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is CVE-2023-4809?
In pf packet processing with a 'scrub fragment reassemble' rule, a packet containing multiple IPv6 fragment headers would be reassembled, and then immediately processed. That is, a packet with multiple fragment extension headers would not be recognized as the correct ultimate payload. Instead a packet with multiple IPv6 fragment headers would unexpectedly be interpreted as a fragmented packet, rather than as whatever the real payload is. As a result, IPv6 fragments may bypass pf firewall rules written on the assumption all fragments have been reassembled and, as a result, be forwarded or processed by the host.
How severe is CVE-2023-4809?
CVE-2023-4809 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.68% probability of exploitation in the next 30 days.
How do I fix CVE-2023-4809?
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