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Fencer Vulns
low 3.3

CVE-2021-36087 json

The CIL compiler in SELinux 3.2 has a heap-based buffer over-read in ebitmap_match_any (called indirectly from cil_check_neverallow).

published 2021-07-01 5 y ago modified 2026-10-14 25 d ago also EUVD-2021-22720

cvss
3.3
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 41%
public exploits
0
none known

Summary

The CIL compiler in SELinux 3.2 has a heap-based buffer over-read in ebitmap_match_any (called indirectly from cil_check_neverallow). This occurs because there is sometimes a lack of checks for invalid statements in an optional block.

Patch / fix

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.5
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • Siemens RUGGEDCOM ROX MX5000 V2.17.0
  • Siemens RUGGEDCOM ROX MX5000RE V2.17.0
  • Siemens RUGGEDCOM ROX RX1400 V2.17.0
  • Siemens RUGGEDCOM ROX RX1500 V2.17.0
  • Siemens RUGGEDCOM ROX RX1501 V2.17.0
  • Siemens RUGGEDCOM ROX RX1510 V2.17.0
  • Siemens RUGGEDCOM ROX RX1511 V2.17.0
  • Siemens RUGGEDCOM ROX RX1512 V2.17.0
  • Siemens RUGGEDCOM ROX RX1524 V2.17.0
  • Siemens RUGGEDCOM ROX RX1536 V2.17.0
  • Siemens RUGGEDCOM ROX RX5000 V2.17.0
  • libsepol Debian 14, Debian 13, Debian 12 3.3-1

debian advisories DEBIAN-CVE-2021-36087

  • libsepol Ubuntu 18.04 LTS 2.7-1ubuntu0.1
  • libsepol Ubuntu 20.04 LTS 3.0-1ubuntu0.1
  • libsepol Ubuntu Pro 16.04 LTS 2.4-2ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2021-36087

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libsepol RHEL 8 2.9-3.el8

red hat advisories RHSA-2021:4513

  • libsepol AlmaLinux 8 2.9-3.el8

almalinux advisories ALSA-2021:4513

  • libsepol Rocky Linux 8 2.9-3.el8

rocky linux advisories RLSA-2021:4513

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-36087 updated cvss 3.3

libsepol: heap-based buffer overflow in ebitmap_match_any()

  • Red Hat Enterprise Linux 7 libsepol
    affected: no fix available “Fix deferred”
  • Red Hat CodeReady Linux Builder (v. 8) libsepol-static 2.9-3.el8, libsepol-debuginfo 2.9-3.el8, libsepol-debugsource 2.9-3.el8 Red Hat Enterprise Linux BaseOS (v. 8) libsepol 2.9-3.el8
    fixed: vendor fix RHSA-2021:4513
  • Red Hat Enterprise Linux 6 libsepol Red Hat Enterprise Linux 9 libsepol, libsepol-utils
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-23-348-10 updated cvss 3.3

Siemens SIMATIC S7-1500

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.0, < 3.1.5
    affected: fixed in V3.1.5, mitigation support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

Exploit prediction

0.47% chance of exploitation in the next 30 days, higher than 41% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • bugs.chromium.org https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=32675 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 3.3 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
NVD 2.0 2.1 AV:L/AC:L/Au:N/C:N/I:N/A:P

Affected products

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens RUGGEDCOM ROX MX5000
  • Siemens RUGGEDCOM ROX MX5000RE
  • Siemens RUGGEDCOM ROX RX1400
  • Siemens RUGGEDCOM ROX RX1500
  • Siemens RUGGEDCOM ROX RX1501
  • Siemens RUGGEDCOM ROX RX1510
  • Siemens RUGGEDCOM ROX RX1511
  • Siemens RUGGEDCOM ROX RX1512
  • Siemens RUGGEDCOM ROX RX1524
  • Siemens RUGGEDCOM ROX RX1536
  • Siemens RUGGEDCOM ROX RX5000

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.