Skip to content
CVE Ledger
  • Newest CVEsPage
  • Recently added to KEVPage
  • Rising exploitation (EPSS)Page
  • Weekly digestPage
  • StatisticsPage
  • WatchlistPage
  • API docsPage
  • MCP serverPage
  • AboutPage
  • Data sourcesPage
  • Data statusPage
  • ChangelogPage
  • How it's builtPage
  • Support the projectPage

14 results

Back

CVE-2026-4247TCP: remotely exploitable DoS vector (mbuf leak)

Description

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.

Timeline

  1. ID reserved

    By freebsd

  2. · 10 days later

    Published

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2026-4247, by who scored it
Scored byCVSSScoreVector
CISA-ADPADP (enrichment)3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVDNVD · Analyzed3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS (exploitation in 30 days)
1.2% · top 32% of all CVEs (12 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: yes · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.

Affected products

  • FreeBSD · FreeBSD

    • affected 15.0-RELEASE – < p5
    • affected 14.4-RELEASE – < p1
    • affected 14.3-RELEASE – < p10

References

References1

Sources

The same CVE in the primary databases and aggregators, to check against.

Badge for a README or a ticket

CVE-2026-4247 badge
[![CVE-2026-4247](https://cveledger.app/badge/CVE-2026-4247.svg)](https://cveledger.app/cve/CVE-2026-4247)

Record last updated .