CVE-2025-21955: ksmbd: prevent connection release during oplock break notification
Vulnerability summary
CVE-2025-21955 is a high (CVSS 8.8) vulnerability in linux. EPSS estimates a 0.50% chance of exploitation in the next 30 days, higher than 43% of scored vulnerabilities.
Not severe (CVSS 8.8, network access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 20 · Related 18Timeline
- 01-04-2025PublishedVulnerability first disclosed.
- 30-10-2026Last modifiedVulnerability information updated.
Description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: prevent connection release during oplock break notification ksmbd_work could be freed when after connection release. Increment r_count of ksmbd_conn to indicate that requests are not finished yet and to not release the connection.
CVSS metrics
5 scores · 4 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated8.8HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HDiffers
- NVDNIST5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HDiffers
EPSS trend
Probability
0.50%
Chance of exploitation in the next 30 days
Percentile
43%
Versus all other CVEs
30-day change
Increase +0.01 pp
From 0.50% 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, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu126 products
- linuxAll versions (No fix recorded) | < 6.8.0-84.84
- linux-allwinner-5.19All versions (No fix recorded)
- linux-awsAll versions (No fix recorded) | < 6.8.0-1039.41
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ 0626e6641f6b467447c81dd7678a69c66f7746cf, < 8e6508c7ecb1802909f294827eff38f301d0c937 | ≥ 0626e6641f6b467447c81dd7678a69c66f7746cf, < 09aeab68033161cb54f194da93e51a11aee6144b | ≥ 0626e6641f6b467447c81dd7678a69c66f7746cf, < a4261bbc33fbf99b99c80aa3a2c5097611802980 | ≥ 0626e6641f6b467447c81dd7678a69c66f7746cf, < f17d1c63a76b0fe8e9c78023a86507a3a6d62cfa | ≥ 0626e6641f6b467447c81dd7678a69c66f7746cf, < 3aa660c059240e0c795217182cf7df32909dd917 | 5.15
- linux_kernel≥ 5.15, < 6.6.84 | ≥ 6.7, < 6.12.20 | ≥ 6.13, < 6.13.8 | 6.14:rc1 | 6.14:rc2 | 6.14:rc3 | 6.14:rc4 | 6.14:rc5 | 6.14:rc6
Debian1 product
- linuxAll versions (No fix recorded) | < 6.12.20-1
3 vendors · 129 products
