CVE-2026-64257: smb: client: reject overlapping data areas in SMB2 responses
Vulnerability summary
CVE-2026-64257 is a critical (CVSS 9.1) vulnerability in linux. EPSS estimates a 0.70% chance of exploitation in the next 30 days, higher than 53.2% of scored vulnerabilities.
Severe, CVSS 9.1 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 1% (FIRST, 03-11-2026)
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 7 · Related 7Timeline
- 25-07-2026PublishedVulnerability first disclosed.
- 17-08-2026Last modifiedVulnerability information updated.
Description
In the Linux kernel, the following vulnerability has been resolved: smb: client: reject overlapping data areas in SMB2 responses Commit 53b7c271f06b ("smb: client: restrict implied bcc[0] exemption to responses without data area") restricted the implied bcc[0] length exception to responses without a data area. However, the overlap handling in __smb2_calc_size() clears data_length, which can make an invalid response appear to have no data area and so qualify for the exception. Track data area overlap separately and reject such responses before applying the length compatibility exceptions.
CVSS metrics
4 scores · 3 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated9.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- NVDNIST9.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
EPSS trend
Probability
0.70%
Chance of exploitation in the next 30 days
Percentile
53%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.70% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeNo weakness data has been published for this record.
Affected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu120 products
- linuxAll versions (No fix recorded)
- linux-allwinner-5.19All versions (No fix recorded)
- linux-awsAll versions (No fix recorded)
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ 31c6312608c60b72a1feb99a5afb680645a3e8a3, < 445ece263131780dee273d727a4d6f11934feec7 | ≥ 573e502d14714d2947e22e7eff40ec20a6a44a42, < 36bfa52459e45c0d5b668de2f1c91f6dc5c67775 | ≥ 419ec1b604d7fb60c10aec2dc062371f9fcd4940, < 4a9d2657d3e05f6ed09c148cb127b4e58702275f | ≥ ceb875a375dedbf51c9425c1d13a2d7a8435c08c, < fdafa1e68dc75045b7b617e6e7d2854950804d83 | ≥ 6e9d10f62773b99bd927940fd9cbdfe7207e23ff, < 57cba95f0e97c6f6e45e6731da30aff091bd7460 | ≥ 53b7c271f06be4dd5cfc8c6ef552a8355c891a7f, < 8986c932905ea508d66da421eb2eb6e676ace1fe | 8d0bbc78046d264bbf6a574ea6f9072258a43e35 | b6a381c01e2ac98a48e32ac0f2a45bbadd9e26b0 | ≥ 5.10.261, < 5.11 | ≥ 5.15.212, < 5.16
- linux_kernel≥ 5.10.261, < 5.11 | ≥ 5.15.212, < 5.16 | 7.2:rc3
2 vendors · 122 products