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TI-2026-03694 Aliases CVE-2026-4247GHSA-374j-38xh-4wr2

TCP: remotely exploitable DoS vector (mbuf leak)

Priority MEDIUM 41CWE-401Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA. Impact type from CWE-401.

Summary

When a challenge ACK is to be sent tcp_respond() constructs and sends the challenge ACK and consumes the mbuf that is passed in. When no challenge ACK should be sent the function returns and leaks the mbuf. If an attacker is either on path with an established TCP connection, or can themselves establish a TCP connection, to an affected FreeBSD machine, they can easily craft and send packets which meet the challenge ACK criteria and cause the FreeBSD host to leak an mbuf for each crafted packet in excess of the configured rate limit settings i.e. with default settings, crafted packets in excess of the first 5 sent within a 1s period will leak an mbuf. Technically, off-path attackers can also exploit this problem by guessing the IP addresses, TCP port numbers and in some cases the sequence numbers of established connections and spoofing packets towards a FreeBSD machine, but this is harder to do effectively.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.01141 66th percentileScored 2026-11-07
Fix Fixed FreeBSD (FreeBSD): p5, p1, p10

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
FreeBSDFreeBSD15.0-RELEASE to before p5; 14.4-RELEASE to before p1; 14.3-RELEASE to before p10p5, p1, p10Patch availableCNA
  • FreeBSD VendorFreeBSD Affected 15.0-RELEASE to before p5; 14.4-RELEASE to before p1; 14.3-RELEASE to before p10 Fixed in p5, p1, p10 Patch available CNA

CPE configurations NVD · 17

CPEVersionsRoleVendor
cpe:2.3:o:freebsd:freebsd:14.3:-:*:*:*:*:*:*14.3VulnerableFreeBSD
cpe:2.3:o:freebsd:freebsd:14.3:p1:*:*:*:*:*:*14.3 p1VulnerableFreeBSD
cpe:2.3:o:freebsd:freebsd:14.3:p2:*:*:*:*:*:*14.3 p2VulnerableFreeBSD
cpe:2.3:o:freebsd:freebsd:14.3:p3:*:*:*:*:*:*14.3 p3VulnerableFreeBSD
cpe:2.3:o:freebsd:freebsd:14.3:p4:*:*:*:*:*:*14.3 p4VulnerableFreeBSD
cpe:2.3:o:freebsd:freebsd:14.3:p5:*:*:*:*:*:*14.3 p5VulnerableFreeBSD
cpe:2.3:o:freebsd:freebsd:14.3:p6:*:*:*:*:*:*14.3 p6VulnerableFreeBSD
cpe:2.3:o:freebsd:freebsd:14.3:p7:*:*:*:*:*:*14.3 p7VulnerableFreeBSD
cpe:2.3:o:freebsd:freebsd:14.3:p8:*:*:*:*:*:*14.3 p8VulnerableFreeBSD
cpe:2.3:o:freebsd:freebsd:14.3:p9:*:*:*:*:*:*14.3 p9VulnerableFreeBSD
  • cpe:2.3:o:freebsd:freebsd:14.3:-:*:*:*:*:*:* Versions 14.3 Vulnerable ·FreeBSD
  • cpe:2.3:o:freebsd:freebsd:14.3:p1:*:*:*:*:*:* Versions 14.3 p1 Vulnerable ·FreeBSD
  • cpe:2.3:o:freebsd:freebsd:14.3:p2:*:*:*:*:*:* Versions 14.3 p2 Vulnerable ·FreeBSD
  • cpe:2.3:o:freebsd:freebsd:14.3:p3:*:*:*:*:*:* Versions 14.3 p3 Vulnerable ·FreeBSD
  • cpe:2.3:o:freebsd:freebsd:14.3:p4:*:*:*:*:*:* Versions 14.3 p4 Vulnerable ·FreeBSD
  • cpe:2.3:o:freebsd:freebsd:14.3:p5:*:*:*:*:*:* Versions 14.3 p5 Vulnerable ·FreeBSD
  • cpe:2.3:o:freebsd:freebsd:14.3:p6:*:*:*:*:*:* Versions 14.3 p6 Vulnerable ·FreeBSD
  • cpe:2.3:o:freebsd:freebsd:14.3:p7:*:*:*:*:*:* Versions 14.3 p7 Vulnerable ·FreeBSD
  • cpe:2.3:o:freebsd:freebsd:14.3:p8:*:*:*:*:*:* Versions 14.3 p8 Vulnerable ·FreeBSD
  • cpe:2.3:o:freebsd:freebsd:14.3:p9:*:*:*:*:*:* Versions 14.3 p9 Vulnerable ·FreeBSD
Show 7 more CPE
CPEVersionsRoleVendor
cpe:2.3:o:freebsd:freebsd:14.4:-:*:*:*:*:*:*14.4VulnerableFreeBSD
cpe:2.3:o:freebsd:freebsd:14.4:rc1:*:*:*:*:*:*14.4 rc1VulnerableFreeBSD
cpe:2.3:o:freebsd:freebsd:15.0:-:*:*:*:*:*:*15.0VulnerableFreeBSD
cpe:2.3:o:freebsd:freebsd:15.0:p1:*:*:*:*:*:*15.0 p1VulnerableFreeBSD
cpe:2.3:o:freebsd:freebsd:15.0:p2:*:*:*:*:*:*15.0 p2VulnerableFreeBSD
cpe:2.3:o:freebsd:freebsd:15.0:p3:*:*:*:*:*:*15.0 p3VulnerableFreeBSD
cpe:2.3:o:freebsd:freebsd:15.0:p4:*:*:*:*:*:*15.0 p4VulnerableFreeBSD
  • cpe:2.3:o:freebsd:freebsd:14.4:-:*:*:*:*:*:* Versions 14.4 Vulnerable ·FreeBSD
  • cpe:2.3:o:freebsd:freebsd:14.4:rc1:*:*:*:*:*:* Versions 14.4 rc1 Vulnerable ·FreeBSD
  • cpe:2.3:o:freebsd:freebsd:15.0:-:*:*:*:*:*:* Versions 15.0 Vulnerable ·FreeBSD
  • cpe:2.3:o:freebsd:freebsd:15.0:p1:*:*:*:*:*:* Versions 15.0 p1 Vulnerable ·FreeBSD
  • cpe:2.3:o:freebsd:freebsd:15.0:p2:*:*:*:*:*:* Versions 15.0 p2 Vulnerable ·FreeBSD
  • cpe:2.3:o:freebsd:freebsd:15.0:p3:*:*:*:*:*:* Versions 15.0 p3 Vulnerable ·FreeBSD
  • cpe:2.3:o:freebsd:freebsd:15.0:p4:*:*:*:*:*:* Versions 15.0 p4 Vulnerable ·FreeBSD

Remediation

  • Fix · CNA FreeBSD (FreeBSD) Fixed in p5, p1, p10

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-4247
  2. 2026-10-03 Alias added: GHSA-374j-38xh-4wr2

References

Advisory 1

  • TI-2011-04182 Buffer overflow in libtelnet/encrypt.c in telnetd in FreeBSD 7.3 through 9.0, MIT… CVSS 2.0HIGH 10.0
  • TI-2007-03684 Integer overflow in print-bgp.c in the BGP dissector in tcpdump 3.9.6 and earlier allows… CVSS 3.1CRITICAL 9.8
  • TI-2002-00376 Integer overflow in xdr_array function in RPC servers for operating systems that use… CVSS 3.1CRITICAL 9.8
  • TI-2024-05929 Openssh: regresshion - race condition in ssh allows rce/dos CVSS 3.1HIGH 8.1
  • TI-2003-00437 Off-by-one error in the fb_realpath() function, as derived from the realpath function in… CVSS 3.1CRITICAL 9.8
  • TI-2003-00642 The prescan function in Sendmail 8.12.9 allows remote attackers to execute arbitrary code… CVSS 2.0HIGH 10.0
See all 576 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences