Linux Kernel up to 7.1.12/7.2.2 TCP tcp_select_initial_window divide by zero

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
7.2$0-$5k0.00

Summaryinfo

A vulnerability categorized as critical has been discovered in Linux Kernel up to 7.1.12/7.2.2. This issue affects the function tcp_select_initial_window of the component TCP. The manipulation results in divide by zero. This vulnerability is reported as CVE-2026-80847. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability classified as critical has been found in Linux Kernel up to 7.1.12/7.2.2. Affected is the function tcp_select_initial_window of the component TCP. The manipulation with an unknown input leads to a divide by zero vulnerability. CWE is classifying the issue as CWE-369. The product divides a value by zero. This is going to have an impact on availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: tcp: clamp route advmss to TCP_MIN_MSS tcp_select_initial_window() assumes that callers never pass an MSS smaller than 1, but route-derived advmss values can violate that assumption. A too-small explicit RTAX_ADVMSS is one way to get there, but it is not the only one. The same divide-by-zero can also be reached through the "default advmss" path when RTAX_ADVMSS is left at 0 and the effective advmss is later driven down by route MTU and min_adv_mss. Introduce a tcp_dst_advmss() helper that clamps route advmss to TCP_MIN_MSS before TCP consumes it, and use it in the TCP paths that derive advmss from dst metrics. This keeps the effective MSS from dropping to zero before tcp_select_initial_window() rounds the receive window.

The advisory is shared for download at git.kernel.org. This vulnerability is traded as CVE-2026-80847 since 08/26/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. 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 09/04/2026). The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 7.1.13, 7.2.3 or 7.3-rc1 eliminates this vulnerability. Applying the patch 6b8c20bf61924dfc38fefb145c9f7406d73fae53/31cf2349361902769dc323e4dbf4b449795ec288/870a9e42ecc6fe1b8c25d87af043cb0d9c178fe1 is able to eliminate this problem.

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

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.5
VulDB Meta Temp Score: 7.2

VulDB Base Score: 7.5
VulDB Temp Score: 7.2
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
💳💳💳💳💳💳
💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock

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

Exploitinginfo

Class: Divide by zero
CWE: CWE-369 / CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-DayUnlockUnlockUnlockUnlock
TodayUnlockUnlockUnlockUnlock

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 7.1.13/7.2.3/7.3-rc1
Patch: 6b8c20bf61924dfc38fefb145c9f7406d73fae53/31cf2349361902769dc323e4dbf4b449795ec288/870a9e42ecc6fe1b8c25d87af043cb0d9c178fe1

Timelineinfo

08/26/2026 CVE reserved
09/04/2026 +9 days Advisory disclosed
09/04/2026 +0 days VulDB entry created
09/04/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-80847 (🔒)
GCVE (CVE): GCVE-0-2026-80847
GCVE (VulDB): GCVE-100-398952

Entryinfo

Created: 09/04/2026 18:31
Changes: 09/04/2026 18:31 (59)
Complete: 🔍
Cache ID: 216::103

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

Discussion

No comments yet. Languages: en.

Please log in to comment.

◂ PreviousOverviewNext ▸

Do you know our Splunk app?

Download it now for free!