Linux Kernel up to 6.6.152/6.12.104/6.18.45/7.1.9 MPTCP Fast Open mptcp_fastopen_subflow_synack_set_params state issue

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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9.5$5k-$25k1.21-

Summaryinfo

A vulnerability classified as very critical has been found in Linux Kernel up to 6.6.152/6.12.104/6.18.45/7.1.9. This issue affects the function mptcp_fastopen_subflow_synack_set_params of the component MPTCP Fast Open. This manipulation causes state issue. This vulnerability is registered as CVE-2026-80585. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 6.6.152/6.12.104/6.18.45/7.1.9 and classified as very critical. Affected by this vulnerability is the function mptcp_fastopen_subflow_synack_set_params of the component MPTCP Fast Open. The manipulation with an unknown input leads to a state issue vulnerability. The CWE definition for the vulnerability is CWE-371. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: mptcp: fastopen: only mark MPTFO subflows with SYN data Passive TCP Fast Open accepts a valid-cookie SYN even when it carries no data. In that case the child socket's receive queue is intentionally left empty. mptcp_fastopen_subflow_synack_set_params() set is_mptfo before checking for queued SYN data. That made data-less TFO SYNs hit a WARN and, if the warning was non-fatal, left stale MPTFO state behind. The stale flag could later trigger a state-confusion bug in check_fully_established(). Only mark the subflow as MPTFO after confirming that an SKB was queued. Return quietly when the receive queue is empty. Note that mptcp_subflow_context's is_mptfo field is now not just about subflows where the TFO was present, but about MPTFO subflow that consumed SYN data. Only having a valid cookie but not carrying data is not really "doing TFO".

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2026-80585 since 08/26/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details are known, but no exploit is available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 08/26/2026).

Upgrading to version 6.6.153, 6.12.105, 6.18.46 or 7.1.10 eliminates this vulnerability. Applying the patch f75f174edc865738522e514d042cf5627f084859/fca7e444c04689fe4cc6b56f2725f804a4bb1ef9/75e564b2ced1cc3d9a8904c7d2d2bb448fffb8b5/72b4a0c51a4b550d40301d60a366b429b8c8e78d/e00b63056fb4f261455b3e5df5268a1f8ce47a87 is able to eliminate this problem.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 10.0
VulDB Meta Temp Score: 9.5

VulDB Base Score: 10.0
VulDB Temp Score: 9.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: State issue
CWE: CWE-371
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.6.153/6.12.105/6.18.46/7.1.10
Patch: f75f174edc865738522e514d042cf5627f084859/fca7e444c04689fe4cc6b56f2725f804a4bb1ef9/75e564b2ced1cc3d9a8904c7d2d2bb448fffb8b5/72b4a0c51a4b550d40301d60a366b429b8c8e78d/e00b63056fb4f261455b3e5df5268a1f8ce47a87

Timelineinfo

08/26/2026 Advisory disclosed
08/26/2026 +0 days CVE reserved
08/26/2026 +0 days VulDB entry created
08/26/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-80585 (🔒)
GCVE (CVE): GCVE-0-2026-80585
GCVE (VulDB): GCVE-100-395905

Entryinfo

Created: 08/26/2026 18:12
Changes: 08/26/2026 18:12 (59)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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