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NVD / CVE Program· CNA Linux

CVE-2026-68118: tcp: challenge ACK for non-exact RST in SYN-RECEIVED

Noroxi assessment

Priority: Monitor (action score 32/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.40% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: Linux Linux 0fe4636665d14a258de70b4f3e8248e6d42038f1, 22cec809b048495310f206d9abbcdbbfbdce3ae3, 234f9ffbd9b2c1b24ec67200ea3cff07401bec48; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 6.6.157.1-1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 0fe4636665d14a258de70b4f3e8248e6d42038f1, 22cec809b048495310f206d9abbcdbbfbdce3ae3, 234f9ffbd9b2c1b24ec67200ea3cff07401bec48; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 6.6.157.1-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: tcp: challenge ACK for non-exact RST in SYN-RECEIVED The SYN-RECEIVED request-socket path in tcp_check_req() accepts an in-window RST without requiring SEG.SEQ to exactly match RCV.NXT. A non-exact RST therefore removes the request instead of eliciting a challenge ACK. RFC 9293 section 3.10.7.4 applies the RFC 5961 reset check in SYN-RECEIVED: an exact RST resets the connection, while a non-exact in-window RST must trigger a challenge ACK and be dropped. Apply that check before the ACK-field validation, following the RFC sequence-number, RST, then ACK processing order. Factor the per-netns challenge ACK quota out of tcp_send_challenge_ack() so request sockets can share it. Use the request socket's send_ack() callback and its own out-of-window ACK timestamp to send and rate-limit the response.

HighCVSS 8.2 · v3.1—No exploit Fix available
Published
Aug 10, 2026
Updated
Oct 30, 2026
EPSS
0.4% · 35th percentile

Report tools

JSON

Action score

32

Monitor

Low priority for now.

CVSS
32 / 40 · 8.2 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
8.2
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 86791bbfe5ed7b275be040cfeff049a1624af1b7, 61f69dc4e40e41b0018f00fa4aeb23d3239556fb, 34fb350281ced2a72707a5c0064f69992d440edb, 3.6affected
    • 282f23c6ee343126156dd41218b22ece96d747e3 and later · before c5dc463cc60eb26079b19607c9dbda76491dad05affected · git
    • 282f23c6ee343126156dd41218b22ece96d747e3 and later · before 8b0a3a094f4cae2fb92e4d08d4eef7246a9d9c49affected · git
    • 282f23c6ee343126156dd41218b22ece96d747e3 and later · before 0fe4636665d14a258de70b4f3e8248e6d42038f1affected · git
    • 282f23c6ee343126156dd41218b22ece96d747e3 and later · before 234f9ffbd9b2c1b24ec67200ea3cff07401bec48affected · git
    • 282f23c6ee343126156dd41218b22ece96d747e3 and later · before 22cec809b048495310f206d9abbcdbbfbdce3ae3affected · git
    • 282f23c6ee343126156dd41218b22ece96d747e3 and later · before a28c4fcbf774e23b4779cae468e3497a5ad1f4a1affected · git
    • 3.0.58 and later · before 3.1affected · semver
    • 3.2.37 and later · before 3.3affected · semver
    • 3.4.25 and later · before 3.5affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:12linux-6.12before 6.12.107-1~deb12u16.12.107-1~deb12u1
Debian:13linuxbefore 6.12.105-16.12.105-1
Debian:14linuxbefore 7.1.6-17.1.6-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-68116Aug 10, 2026 · vxlan: mdb: Fix source list corruption on a failed replace
    31Monitor
  • ← EarlierCVE-2026-68117Aug 10, 2026 · tipc: clear sock->sk on the failed-insert path in tipc_sk_create()
    39Monitor
  • Later →CVE-2026-68121Aug 10, 2026 · pppoe: reload header pointer after dev_hard_header()
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux0fe4636665d14a258de70b4f3e8248e6d42038f1Vendor (CNA)
Linux Linux22cec809b048495310f206d9abbcdbbfbdce3ae3Vendor (CNA)
Linux Linux234f9ffbd9b2c1b24ec67200ea3cff07401bec48Vendor (CNA)
Linux Linux3.1Vendor (CNA)
Linux Linux3.3Vendor (CNA)
Linux Linux3.5Vendor (CNA)
Linux Linux8b0a3a094f4cae2fb92e4d08d4eef7246a9d9c49Vendor (CNA)
Linux Linuxa28c4fcbf774e23b4779cae468e3497a5ad1f4a1Vendor (CNA)
Linux Linuxc5dc463cc60eb26079b19607c9dbda76491dad05Vendor (CNA)
azl3 kernel 6.6.152.1-1 on Azure Linux 3.06.6.157.1-1 · Release NotesMicrosoft (MSRC)
debian:linux6.12.105-1 · Debian:13Package registry (OSV)
debian:linux-6.126.12.107-1~deb12u1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-681540 days apartlibceph: reject zero bucket types in crush_decode
    39Monitor
  • CVE-2026-684775 days apartipvs: fix more places with wrong ipv6 transport offsets
    39Monitor
  • CVE-2026-720655 days apartnet: mana: Validate the packet length reported by the NIC
    39Monitor
  • CVE-2026-9999966 days apartipv4: validate checksum_start before completing checksum
    37Monitor
  • CVE-2026-681990 days apartwifi: ath6kl: fix OOB access from firmware ADDBA window size
    35Monitor
  • CVE-2026-684543 days apartKVM: s390: pci: Fix handling of AIF enable without AISB
    35Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
low · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
Low
Availability impact
High

Weakness class (CWE)

CWE-20 · Improper Input Validation

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records