8.4

CVE-2026-63952: memfd: deny writeable mappings when implying SEAL_WRITE

Analyzed
AliasesUBUNTU-CVE-2026-63952DEBIAN-CVE-2026-63952
Published 19-07-2026Last modified 19-10-2026

Vulnerability summary

CVE-2026-63952 is a high (CVSS 8.4) vulnerability in linux. EPSS estimates a 0.13% chance of exploitation in the next 30 days, higher than 2.4% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 8.4, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
8.4/10
010
High · v3.1 (CVE.org)
EPSS score
0.13%
0%100%
Low · -0.04 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 32 · Related 28
OPENSUSE-SU-2026:21555-1RHSA-2026:57251RHSA-2026:57252RHSA-2026:67720RHSA-2026:69089SUSE-SU-2026:23066-1

Timeline

  1. 19-07-2026
    PublishedVulnerability first disclosed.
  2. 19-10-2026
    Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: memfd: deny writeable mappings when implying SEAL_WRITE When SEAL_EXEC is added, SEAL_WRITE is implied to make W^X. But the implied seal is set after the check that makes sure the memfd can not have any writable mappings. This means one can use SEAL_EXEC to apply SEAL_WRITE while having writeable mappings. This breaks the contract that SEAL_WRITE provides and can be used by an attacker to pass a memfd that appears to be write sealed but can still be modified arbitrarily. Fix this by adding the implied seals before the call for mapping_deny_writable() is done.

CVSS metrics

5 scores · 4 sources · 2 versions

EPSS trend

Probability

0.13%

Chance of exploitation in the next 30 days

Percentile

2%

Versus all other CVEs

30-day change

Decrease -0.04 pp

From 0.16% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu140 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)
Linux2 products
  • linux≥ c4f75bc8bd6b3d62665e1f5400c419540edb5601, < b3f4f82d1315f1439059a83d1c22c51a5b43d99e | ≥ c4f75bc8bd6b3d62665e1f5400c419540edb5601, < 3be2a24f7f72ad7321ed6ad1715b956a4527bcf4 | ≥ c4f75bc8bd6b3d62665e1f5400c419540edb5601, < 0995d1f79aed8ccbf62056189dd53fd19726ea08 | ≥ c4f75bc8bd6b3d62665e1f5400c419540edb5601, < 555702282d4536a865dfffb1cd4f6028f196e7e8 | ≥ c4f75bc8bd6b3d62665e1f5400c419540edb5601, < 3b041514cb6eae45869b020f743c14d983363222 | 6.3
  • linux_kernel≥ 6.3, < 6.6.143 | ≥ 6.7, < 6.12.93 | ≥ 6.13, < 6.18.35 | ≥ 6.19, < 7.0.12 | 7.1:rc1 | 7.1:rc2 | 7.1:rc3 | 7.1:rc4 | 7.1:rc5
Debian1 product
  • linux< 6.12.94-1 | < 7.0.12-1

3 vendors · 143 products

References

24 links
Show all 24 references