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

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于batman-adv tp_meter模块中的除零问题，即当cwnd为0x20000000时计算导致除数为零。

AI Predicted 5.5 Difficulty: Moderate EPSS 0.17% · P7

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 33a3bb4a3345bb511f9c69c913da95d4693e2a4e< 35264c4d46067d6312871488c810cef387f8c1f6 affected
33a3bb4a3345bb511f9c69c913da95d4693e2a4e< 1381b021bf886b793fa5ffb895a8efae7ba0318f affected
33a3bb4a3345bb511f9c69c913da95d4693e2a4e< d08b69da40a101df1e28bfe1e8fa7a09ffa41107 affected
33a3bb4a3345bb511f9c69c913da95d4693e2a4e< cd74176cf1685f35a2e5f212d15748bbfecb53b6 affected
33a3bb4a3345bb511f9c69c913da95d4693e2a4e< ac229c86e49fdb96d91f51bc2fa37a9c4f58c44f affected
33a3bb4a3345bb511f9c69c913da95d4693e2a4e< 7d2a44bc6bbe39aed03c68864aa0e54e04a50278 affected
33a3bb4a3345bb511f9c69c913da95d4693e2a4e< 585616dab0aa9c45bc11b2c8082ca78533bc00e9 affected
33a3bb4a3345bb511f9c69c913da95d4693e2a4e< 33ccd52f3cc9ed46ce395199f89aa3234dc83314 affected
… +10 more rows
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I. Basic Information for CVE-2026-63836

Vulnerability Information
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Vulnerability Title
batman-adv: tp_meter: avoid divide-by-zero for dec_cwnd
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于batman-adv tp_meter模块中的除零问题，即当cwnd为0x20000000时计算导致除数为零。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 33a3bb4a3345bb511f9c69c913da95d4693e2a4e ~ 35264c4d46067d6312871488c810cef387f8c1f6 -
Linux Linux 4.8 -

II. Public POCs for CVE-2026-63836

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III. Intelligence Information for CVE-2026-63836

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Patches & Fixes for CVE-2026-63836 (6)

Same Patch Batch · Linux · 2026-07-19 · 429 CVEs total

CVE-2026-63795 10.0 CRITICAL 9p: avoid putting oldfid in p9_client_walk() error path
CVE-2026-64056 9.8 CRITICAL net: ethernet: cortina: Make RX SKB per-port
CVE-2026-63887 9.8 CRITICAL scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf
CVE-2026-53399 9.8 CRITICAL nfsd: release layout stid on setlease failure
CVE-2026-53398 9.8 CRITICAL NFSD: Fix SECINFO_NO_NAME decode error cleanup
CVE-2026-63984 9.8 CRITICAL ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()
CVE-2026-63886 9.8 CRITICAL scsi: target: iscsi: Validate CHAP_R length before base64 decode
CVE-2026-64035 9.8 CRITICAL igc: set tx buffer type for SMD frames
CVE-2026-64150 9.8 CRITICAL netfilter: nft_inner: release local_lock before re-enabling softirqs
CVE-2026-63924 9.8 CRITICAL ipv6: exthdrs: refresh nh pointer after ipv6_hop_jumbo()
CVE-2026-63979 9.8 CRITICAL net/handshake: hand off the pinned file reference to accept_doit
CVE-2026-63800 9.8 CRITICAL pNFS: Fix use-after-free in pnfs_update_layout()
CVE-2026-64132 9.8 CRITICAL ipv6: ioam: refresh hdr pointer before ioam6_event()
CVE-2026-64037 9.8 CRITICAL wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled
CVE-2026-63978 9.8 CRITICAL net/handshake: Drain pending requests at net namespace exit
CVE-2026-63825 9.8 CRITICAL gcov: use atomic counter updates to fix concurrent access crashes
CVE-2026-64125 9.8 CRITICAL net: bcmgenet: keep RBUF EEE/PM disabled
CVE-2026-63857 9.8 CRITICAL net: airoha: Do not read uninitialized fragment address in airoha_dev_xmit()
CVE-2026-64113 9.8 CRITICAL ixgbevf: fix use-after-free in VEPA multicast source pruning
CVE-2026-64046 9.8 CRITICAL net: tls: prevent chain-after-chain in plain text SG

Showing top 20 of 429 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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