CVE-2026-63836

Service interrupt via congestion-window divisor overflow

Published Jul 19, 2026 · Updated Jul 19, 2026

Divide-by-zero in the batman-adv throughput meter in Linux Kernel allows attackers to cause a service interrupt through ACK processing. In batadv_tp_update_cwnd(), multiplying cwnd by eight in 32-bit unsigned arithmetic wraps 0x20000000 to zero and uses that zero as the divisor. The fault requires throughput-meter ACK handling to reach that maximum congestion-window value; the published record does not identify the attacker's required access.

CVSS severityUnavailable
Unscored
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Divide-by-zero in the batman-adv throughput meter in Linux Kernel allows attackers to cause a service interrupt through ACK processing. In batadv_tp_update_cwnd(), multiplying cwnd by eight in 32-bit unsigned arithmetic wraps 0x20000000 to zero and uses that zero as the divisor. The fault requires throughput-meter ACK handling to reach that maximum congestion-window value; the published record does not identify the attacker's required access.

The record

CVE
CVE-2026-63836
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1499.004
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Jul 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <1381b021bf886b793fa5ffb895a8efae7ba0318f
  2. Affected versionversion=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <33ccd52f3cc9ed46ce395199f89aa3234dc83314
  3. Affected versionversion=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <35264c4d46067d6312871488c810cef387f8c1f6
  4. Affected versionversion=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <585616dab0aa9c45bc11b2c8082ca78533bc00e9
  5. Affected versionversion=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <7d2a44bc6bbe39aed03c68864aa0e54e04a50278
  6. Affected versionversion=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <ac229c86e49fdb96d91f51bc2fa37a9c4f58c44f
  7. Affected versionversion=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <cd74176cf1685f35a2e5f212d15748bbfecb53b6
  8. Affected versionversion=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <d08b69da40a101df1e28bfe1e8fa7a09ffa41107
  9. Affected versionversion=4.8

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linux Kernelversion=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <1381b021bf886b793fa5ffb895a8efae7ba0318f; version=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <33ccd52f3cc9ed46ce395199f89aa3234dc83314; version=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <35264c4d46067d6312871488c810cef387f8c1f6; version=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <585616dab0aa9c45bc11b2c8082ca78533bc00e9; version=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <7d2a44bc6bbe39aed03c68864aa0e54e04a50278; version=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <ac229c86e49fdb96d91f51bc2fa37a9c4f58c44f; version=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <cd74176cf1685f35a2e5f212d15748bbfecb53b6; version=33a3bb4a3345bb511f9c69c913da95d4693e2a4e <d08b69da40a101df1e28bfe1e8fa7a09ffa41107; version=4.8

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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