Unknown

CVE-2026-63836 — batman-adv: tp_meter: avoid divide-by-zero for dec_cwnd

In the Linux kernel, the following vulnerability has been resolved: batman-adv: tp_meter: avoid divide-by-zero for dec_cwnd The cwnd is always MSS <= cwnd <= 0x20000000. But the calculation in batadv_tp_update_cwnd() assumes unsigned 32 bit arithmetics. ((mss * 8) ** 2) / (cwnd * 8) In case cwnd is actually 0x20000000, it will be shifted by 3 bit to the left end up at 0x100000000 or U32_MAX + 1. It will therefore wrap around and be 0 - resulting in: ((mss * 8) ** 2) / 0 This is of course invalid and cannot be calculated. The calculation should must be simplified to avoid this overflow: (mss ** 2) * 8 / cwnd It will keep the precision enhancement from the scaling (by 8) but avoid the overflow in the divisor. In theory, there could still be an overflow in the dividend. It is at the moment fixed to BATADV_TP_PLEN in batadv_tp_recv_ack() - so it is not an imminent problem. But allowing it to use the whole u32 bit range, would mean that it can still use up to 67 bits. To keep this calculation safe for 32 bit arithmetic, mss must never use more than floor((32 - 3) / 2) bits - or in other words: must never be larger than 16383.

Published Jul 19, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+1

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.17%

ahead of 6% of scored CVEs · Oct 15, 2026

Affects

Linux

CVSS base

—

Score not published yet.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ 33a3bb4a3345bb511f9c69c913da95d4693e2a4e and < 35264c4d46067d6312871488c810cef387f8c1f6≥ 33a3bb4a3345bb511f9c69c913da95d4693e2a4e and < 1381b021bf886b793fa5ffb895a8efae7ba0318f≥ 33a3bb4a3345bb511f9c69c913da95d4693e2a4e and < d08b69da40a101df1e28bfe1e8fa7a09ffa41107≥ 33a3bb4a3345bb511f9c69c913da95d4693e2a4e and < cd74176cf1685f35a2e5f212d15748bbfecb53b6≥ 33a3bb4a3345bb511f9c69c913da95d4693e2a4e and < ac229c86e49fdb96d91f51bc2fa37a9c4f58c44f≥ 33a3bb4a3345bb511f9c69c913da95d4693e2a4e and < 7d2a44bc6bbe39aed03c68864aa0e54e04a50278≥ 33a3bb4a3345bb511f9c69c913da95d4693e2a4e and < 585616dab0aa9c45bc11b2c8082ca78533bc00e9≥ 33a3bb4a3345bb511f9c69c913da95d4693e2a4e and < 33ccd52f3cc9ed46ce395199f89aa3234dc83314 and 1 more version 4.8	Vulnerable	CVE Program (cve.org) e CISA ADP

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Not enough vector or weakness data: use the affected application’s logs as a starting point.

application logs

Timeline

What happened to this CVE, newest first.

2026
Record published
Oct 15, 2026
Affected products added · linux/linux
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · → Awaiting Analysis
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Jul 19, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

8 on the record

git.kernel.org/stable/c/7d2a44bc6bbe39aed03c68864aa0e54e04a50278
NIST National Vulnerability Database
git.kernel.org/stable/c/d08b69da40a101df1e28bfe1e8fa7a09ffa41107
NIST National Vulnerability Database
git.kernel.org/stable/c/33ccd52f3cc9ed46ce395199f89aa3234dc83314
NIST National Vulnerability Database
git.kernel.org/stable/c/585616dab0aa9c45bc11b2c8082ca78533bc00e9
NIST National Vulnerability Database
git.kernel.org/stable/c/ac229c86e49fdb96d91f51bc2fa37a9c4f58c44f
NIST National Vulnerability Database
git.kernel.org/stable/c/1381b021bf886b793fa5ffb895a8efae7ba0318f
NIST National Vulnerability Database
git.kernel.org/stable/c/cd74176cf1685f35a2e5f212d15748bbfecb53b6
NIST National Vulnerability Database
git.kernel.org/stable/c/35264c4d46067d6312871488c810cef387f8c1f6
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 20h
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 20h
Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 1d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CVSS score published by NVD, the CNA, CISA or GitHub so far.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-63836 is "batman-adv: tp_meter: avoid divide-by-zero for dec_cwnd", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. EPSS 0.17% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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