Linux Kernel up to 6.6.152/6.12.104/6.18.45/7.1.9 mptcp subflow.c Remote Code Execution

CVSS Meta Temp Score
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CTI Interest Score
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9.5$0-$5k0.30

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.6.152/6.12.104/6.18.45/7.1.9 and classified as very critical. The affected element is an unknown function of the file subflow.c of the component mptcp. Executing a manipulation can lead to Remote Code Execution. This vulnerability is handled as CVE-2026-80587. The attack can be executed remotely. There is not any exploit 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. This vulnerability affects an unknown code of the file subflow.c of the component mptcp. The manipulation with an unknown input leads to a remote code execution vulnerability. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: mptcp: avoid combining some incoming suboptions Some MPTCP suboptions are mutually exclusive according to the RFC8684, but also because in different places, the code doesn't expect some combinations to be present. That's specially true for suboptions that would be present twice, but with different attributes. The new restrictions are the same as the ones applied on the output side, with mptcp_write_options. The same rules can be reused with a small fix: an MP_FASTCLOSE can be used with a DSS when the sender picks this option [1], which is not the case on Linux. Here are the rules: Which options can be used together? X: mutually exclusive O: often used together C: can be used together in some cases P: could be used together but we prefer not to (optimisations) | Opt: | MPC | MPJ | DSS | ADD | RM | PRIO | FAIL | FC | |------|------|------|------|------|------|------|------|------| | MPC |------|------|------|------|------|------|------|------| | MPJ | X |------|------|------|------|------|------|------| | DSS | X | X |------|------|------|------|------|------| | ADD | X | X | P |------|------|------|------|------| | RM | C | C | C | P |------|------|------|------| | PRIO | X | C | C | C | C |------|------|------| | FAIL | X | X | C | X | X | X |------|------| | FC | X | X | P | X | X | X | X |------| | RST | X | X | X | X | X | X | O | O | |------|------|------|------|------|------|------|------|------| The only difference is with the 'P': another stack could send and ADD_ADDR with other suboptions (DSS, RM_ADDR), and this should be allowed. A few points of attention: - In theory, an MP_CAPABLE could be used with a RM_ADDR, but there is no reason to add it with a SYN. Note that even with a 4th ACK, it doesn't seem to be useful, except when IDs are known in advance via another channel. Better not to break that. - Now, combining both an MP_CAPABLE and an MP_JOIN will no longer result to a reject of the two options, but only the second suboption is ignored. That seems OK to do that for this unexpected error. At least now all inconsistent combinations are handled the same way. This could change later in next. This also means the explicit checks for having both MPC + MPJ in subflow.c will now be unreachable. That's fine, they will be removed in a follow-up patch. - In case of conflicting combinations, the extra suboption(s) is/are ignored: having such combinations either means the remote peer is buggy, or is evil. The simplest action is then taken in this case: stop processing the current suboption. - In mp_opt->suboptions, there is also a bit reserved to the checksum, which can be used in an MP_CAPABLE and a DSS. Each time a DSS option can be used in parallel with another option, the checksum can be set, so the verification is combined into a new OPTIONS_MPTCP_DSS macro. - An MP_CAPABLE ACK can carry a Data-Level Length, and an optional Checksum: they are the same as the ones found in a DSS, because a DSS cannot be used in parallel to an MP_CAPABLE. Similarly, even if there is room, a DSS cannot be used with an MP_JOIN.

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2026-80587 since 08/26/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (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 dc1d8d3eb345c616fbe922a010fa391c72c54d52/099bfcbd0c16ae9b50aba2a1bea033e63f895da7/a04dcc784959e4702048785d87e0d029bd2fbdcb/6bab907292155513af397a12ccb488acbfc30d79/b6ee361524641f57b2e2363f7737f20e17f67827 is able to eliminate this problem.

VulDB is the best source for vulnerability data and more expert information about this specific topic.

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: Remote Code Execution
CWE: Unknown
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: dc1d8d3eb345c616fbe922a010fa391c72c54d52/099bfcbd0c16ae9b50aba2a1bea033e63f895da7/a04dcc784959e4702048785d87e0d029bd2fbdcb/6bab907292155513af397a12ccb488acbfc30d79/b6ee361524641f57b2e2363f7737f20e17f67827

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-2026-80587 (🔒)
GCVE (CVE): GCVE-0-2026-80587
GCVE (VulDB): GCVE-100-395896

Entryinfo

Created: 08/26/2026 18:08
Changes: 08/26/2026 18:08 (58)
Complete: 🔍
Cache ID: 216::103

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