8.1

CVE-2026-63909: linux

CVSS: 8.1v3.1HighAwaiting analysis
AliasesUBUNTU-CVE-2026-63909DEBIAN-CVE-2026-63909
Published 19-07-2026Last modified 05-08-2026
Open JSON

Vulnerability summary

CVE-2026-63909 is a high (CVSS 8.1) vulnerability in linux. EPSS estimates a 0.63% chance of exploitation in the next 30 days, higher than 49.1% of scored vulnerabilities.

Overall risk
33/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.1/10
010
High · v3.1 (CVE.org)
EPSS score
0.63%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 14 · Related 14
USN-8593-1USN-8618-1USN-8663-1USN-8664-1USN-8728-1USN-8728-2

Timeline

  1. 19-07-2026
    PublishedVulnerability first disclosed.
  2. 05-08-2026
    Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loops Commit d07b26f39246 ("ksmbd: require minimum ACE size in smb_check_perm_dacl()") introduced a transposed bounds check: if (offsetof(struct smb_ace, sid) + aces_size < CIFS_SID_BASE_SIZE) Since offsetof(..sid) is 8 and CIFS_SID_BASE_SIZE is 8, this evaluates to `aces_size < 0`. Because `aces_size` is always non-negative, this check becomes dead code and never breaks the loop. Worse, that commit removed the old 4-byte guard, meaning the loop now reads `ace->size` (offset 2) even when `aces_size` is 0-3 bytes. This re-opens a 2-byte heap out-of-bounds (OOB) read past the pntsd allocation during subsequent SMB2_CREATE operations. Fix this by properly transposing the comparison to require at least 16 bytes (8-byte offset + 8-byte SID base), matching the correct form used in smb_inherit_dacl().

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.63%

Chance of exploitation in the next 30 days

Percentile

49%

Versus all other CVEs

30-day change

0.00 pp

From 0.63% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.63%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

No weakness data has been published for this record.

Affected systems

Ubuntu132 products
  • linux< 6.8.0-146.146 | < 7.0.0-28.28
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-aws< 6.8.0-1066.69 | < 7.0.0-1009.9
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Debian1 product
  • linux< 6.12.94-1 | < 7.0.12-1
Linux1 product
  • linux≥ 282cbbb476b9f35793452bc461934af4c7eca169, < 5500ba1d410aed1eded3eb04a76b10cfb4409334 | ≥ f20adc4ef7428bc485ee83fd1a592252fb87718b, < f6324b4240cf0b26a84c33f68a1222d727ff4af2 | ≥ 325d4ac11f526cb8964cff14548ccf02d8c756d8, < 0fe08c5776a798f46df1fd74b331be26bdd644d6 | ≥ 95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c, < d333af32e4451285e427f2d9c29de3a39f6f6d48 | ≥ 90089584b2e25c4510b7b987387b4405f0673ece, < 94215d55b09445993929f4fc966061d61de74929 | ≥ 151b1799861fde38087c08f613abc2843ef597b0, < 4f7c131d2bdd7cd64b96f60d10be5ea72253f520 | ≥ d07b26f39246a82399661936dd0c853983cfade7, < 0e60dafe97eca61721f3db456f97d97a80c6c8ae | ≥ 6.6.140, < 6.6.143 | ≥ 6.12.84, < 6.12.93 | ≥ 6.18.25, < 6.18.35 | ≥ 7.0.2, < 7.0.12

3 vendors · 134 products

References

25 links
Show all 25 references