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… (CVE-2026-63836)
A vulnerability in the Linux kernel's batman-adv module related to the tp_meter component could cause a divide-by-zero error in the dec_cwnd calculation. This occurs due to an arithmetic overflow when the congestion window (cwnd) reaches a specific large value, causing the divisor to become zero. The issue arises from incorrect handling of unsigned 32-bit arithmetic in the calculation. The vulnerability has been resolved by simplifying the calculation to avoid overflow while maintaining precision.
AI Analysis
Technical Summary
The Linux kernel's batman-adv module had a vulnerability (CVE-2026-63836) in the tp_meter component where the function batadv_tp_update_cwnd() performed a calculation that could result in a divide-by-zero error. The congestion window (cwnd) value, which ranges from MSS to 0x20000000, was shifted left by 3 bits, causing an overflow beyond the 32-bit unsigned integer limit and wrapping to zero. This led to an invalid division by zero in the formula ((mss * 8) ** 2) / (cwnd * 8). The fix involved simplifying the formula to (mss ** 2) * 8 / cwnd to avoid overflow in the divisor. The calculation remains safe under current constraints on MSS size, preventing potential overflow in the dividend.
Potential Impact
If triggered, the vulnerability could cause a divide-by-zero error in the kernel module, potentially leading to kernel crashes or instability in the batman-adv networking functionality. There is no evidence of known exploits in the wild. The impact is limited to the affected calculation within the kernel's batman-adv tp_meter component.
Mitigation Recommendations
A fix for this vulnerability has been implemented in the Linux kernel by correcting the arithmetic calculation to prevent overflow and divide-by-zero errors. Users should apply the official kernel updates that include this fix once available. Patch status is not yet confirmed in the provided data; check the vendor advisory for current remediation guidance.
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… (CVE-2026-63836)
Description
A vulnerability in the Linux kernel's batman-adv module related to the tp_meter component could cause a divide-by-zero error in the dec_cwnd calculation. This occurs due to an arithmetic overflow when the congestion window (cwnd) reaches a specific large value, causing the divisor to become zero. The issue arises from incorrect handling of unsigned 32-bit arithmetic in the calculation. The vulnerability has been resolved by simplifying the calculation to avoid overflow while maintaining precision.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Linux kernel's batman-adv module had a vulnerability (CVE-2026-63836) in the tp_meter component where the function batadv_tp_update_cwnd() performed a calculation that could result in a divide-by-zero error. The congestion window (cwnd) value, which ranges from MSS to 0x20000000, was shifted left by 3 bits, causing an overflow beyond the 32-bit unsigned integer limit and wrapping to zero. This led to an invalid division by zero in the formula ((mss * 8) ** 2) / (cwnd * 8). The fix involved simplifying the formula to (mss ** 2) * 8 / cwnd to avoid overflow in the divisor. The calculation remains safe under current constraints on MSS size, preventing potential overflow in the dividend.
Potential Impact
If triggered, the vulnerability could cause a divide-by-zero error in the kernel module, potentially leading to kernel crashes or instability in the batman-adv networking functionality. There is no evidence of known exploits in the wild. The impact is limited to the affected calculation within the kernel's batman-adv tp_meter component.
Mitigation Recommendations
A fix for this vulnerability has been implemented in the Linux kernel by correcting the arithmetic calculation to prevent overflow and divide-by-zero errors. Users should apply the official kernel updates that include this fix once available. Patch status is not yet confirmed in the provided data; check the vendor advisory for current remediation guidance.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-f3pj-q27g-923q
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-63836"]
- Ecosystems
- []
- Database Specific Severity
- null
- Cvss Version
- null
Threat ID: 6a5d27ad2a4a8d5989131266
Added to database: 07/19/2026, 19:38:21 UTC
Last enriched: 07/19/2026, 20:18:27 UTC
Last updated: 07/20/2026, 17:26:47 UTC
Views: 9
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