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Fencer Intel
high 7.5

CVE-2021-41991 json

The in-memory certificate cache in strongSwan before 5.9.4 has a remote integer overflow upon receiving many requests with different certif…

published 5y ago modified 4mo ago also EUVD-2021-28981

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
5.3%
EPSS 5.3% chance of exploitation in 30 days, percentile 92%
public exploits
0
none known

Summary

The in-memory certificate cache in strongSwan before 5.9.4 has a remote integer overflow upon receiving many requests with different certificates to fill the cache and later trigger the replacement of cache entries. The code attempts to select a less-often-used cache entry by means of a random number generator, but this is not done correctly. Remote code execution might be a slight possibility.

Patch / fix

  • strongswan strongswan 5.9.4
  • siemens scalance_sc646-2c_firmware 2.3
  • strongswan Debian 14, Debian 13, Debian 12 5.9.4-1

debian advisories DEBIAN-CVE-2021-41991

  • strongswan Ubuntu 18.04 LTS 5.6.2-1ubuntu2.7
  • strongswan Ubuntu 20.04 LTS 5.8.2-1ubuntu3.3
  • strongswan Ubuntu 22.04 LTS 5.9.1-1ubuntu3.1
  • strongswan Ubuntu Pro 14.04 LTS 5.1.2-0ubuntu2.11+esm1
  • strongswan Ubuntu Pro 16.04 LTS 5.3.5-1ubuntu3.8+esm1
  • strongswan Ubuntu Pro FIPS-updates 16.04 LTS 5.3.5-1ubuntu3.fips.3.8.2
  • strongswan Ubuntu Pro FIPS-updates 18.04 LTS 5.6.2-1ubuntu2.fips.2.7.1
  • strongswan Ubuntu Pro FIPS-updates 20.04 LTS 5.8.2-1ubuntu3.fips.3.3.1

ubuntu advisories UBUNTU-CVE-2021-41991

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

  • strongswan SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +7 more 5.8.2-4.14.2
  • strongswan SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +10 more 5.1.3-26.16.1
  • strongswan SLE Workstation Extension 15 SP3, SLE Workstation Extension 15 SP2, SLE Module for Package Hub 15 SP3 +3 more 5.8.2-11.21.1
  • strongswan SLES 11 SP4-LTSS, SLE Point of Sale 11 SP3 4.4.0-6.36.9.1

suse advisories SUSE-SU-2021:3469-1SUSE-SU-2021:3468-1SUSE-SU-2021:3467-1SUSE-SU-2021:14827-1

  • strongswan openSUSE Tumbleweed 5.9.4-1.1
  • strongswan openSUSE Leap 15.2 5.8.2-lp152.2.18.1
  • strongswan openSUSE Leap 15.3 5.8.2-11.21.1

opensuse advisories openSUSE-SU-2024:11655-1openSUSE-SU-2021:1399-1openSUSE-SU-2021:3467-1

  • strongswan Alpine 3.12 5.8.4-r3
  • strongswan Alpine 3.13 5.9.1-r1
  • strongswan Alpine 3.14 5.9.1-r2
  • strongswan Alpine 3.24, Alpine 3.23, Alpine 3.22 +7 more 5.9.1-r3

alpine advisories ALPINE-CVE-2021-41991

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • strongswan CBL-Mariner 2.0 5.9.5-1

azure linux advisories AZL-6897

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

  • strongswan Arch Linux 5.9.4-1

arch linux advisories AVG-2473

Is CVE-2021-41991 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2021-41991 updated cvss 7.5

strongswan: integer overflow when replacing certificates in cache

  • Red Hat Enterprise Linux 7 strongimcv
    affected: no fix planned “Out of support scope”

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-25-259-03 updated cvss 7.5

Siemens SIMATIC NET CP, SINEMA and SCALANCE

  • Siemens RUGGEDCOM RM1224 LTE(4G) EU (6GK6108-4AM00-2BA2) <V7.1 Siemens RUGGEDCOM RM1224 LTE(4G) NAM (6GK6108-4AM00-2DA2) <V7.1 Siemens SCALANCE M804PB (6GK5804-0AP00-2AA2) <V7.1 Siemens SCALANCE M812-1 ADSL-Router (Annex A) (6GK5812-1AA00-2AA2) <V7.1 Siemens SCALANCE M812-1 ADSL-Router (Annex B) (6GK5812-1BA00-2AA2) <V7.1 Siemens SCALANCE M816-1 ADSL-Router (Annex A) (6GK5816-1AA00-2AA2) <V7.1
    +34 more products
    Siemens SCALANCE M816-1 ADSL-Router (Annex B) (6GK5816-1BA00-2AA2) <V7.1 Siemens SCALANCE M826-2 SHDSL-Router (6GK5826-2AB00-2AB2) <V7.1 Siemens SCALANCE M874-2 (6GK5874-2AA00-2AA2) <V7.1 Siemens SCALANCE M874-3 (6GK5874-3AA00-2AA2) <V7.1 Siemens SCALANCE M876-3 (EVDO) (6GK5876-3AA02-2BA2) <V7.1 Siemens SCALANCE M876-3 (ROK) (6GK5876-3AA02-2EA2) <V7.1 Siemens SCALANCE M876-4 (EU) (6GK5876-4AA00-2BA2) <V7.1 Siemens SCALANCE M876-4 (NAM) (6GK5876-4AA00-2DA2) <V7.1 Siemens SCALANCE MUM853-1 (EU) (6GK5853-2EA00-2DA1) <V7.1 Siemens SCALANCE MUM856-1 (EU) (6GK5856-2EA00-3DA1) <V7.1 Siemens SCALANCE MUM856-1 (RoW) (6GK5856-2EA00-3AA1) <V7.1 Siemens SCALANCE S615 (6GK5615-0AA00-2AA2) <V7.1 Siemens SCALANCE SC622-2C (6GK5622-2GS00-2AC2) <V2.3 Siemens SCALANCE SC632-2C (6GK5632-2GS00-2AC2) <V2.3 Siemens SCALANCE SC636-2C (6GK5636-2GS00-2AC2) <V2.3 Siemens SCALANCE SC642-2C (6GK5642-2GS00-2AC2) <V2.3 Siemens SCALANCE SC646-2C (6GK5646-2GS00-2AC2) <V2.3 Siemens SIMATIC CP 1242-7 V2 (6GK7242-7KX31-0XE0) <V3.3.46 Siemens SIMATIC CP 1243-1 (6GK7243-1BX30-0XE0) <V3.3.46 Siemens SIMATIC CP 1243-7 LTE EU (6GK7243-7KX30-0XE0) <V3.3.46 Siemens SIMATIC CP 1243-7 LTE US (6GK7243-7SX30-0XE0) <V3.3.46 Siemens SIMATIC CP 1243-8 IRC (6GK7243-8RX30-0XE0) <V3.3.46 Siemens SIMATIC CP 1542SP-1 (6GK7542-6UX00-0XE0) <V2.2.28 Siemens SIMATIC CP 1542SP-1 IRC (6GK7542-6VX00-0XE0) <V2.2.28 Siemens SIMATIC CP 1543-1 (6GK7543-1AX00-0XE0) <V2.2.28 Siemens SIMATIC CP 1543SP-1 (6GK7543-6WX00-0XE0) <V2.2.28 Siemens SIMATIC CP 1545-1 (6GK7545-1GX00-0XE0) <V1.1 Siemens SINEMA Remote Connect Server <V3.1 Siemens SIPLUS ET 200SP CP 1542SP-1 IRC TX RAIL (6AG2542-6VX00-4XE0) <V2.2.28 Siemens SIPLUS ET 200SP CP 1543SP-1 ISEC (6AG1543-6WX00-7XE0) <V2.2.28 Siemens SIPLUS ET 200SP CP 1543SP-1 ISEC TX RAIL (6AG2543-6WX00-4XE0) <V2.2.28 Siemens SIPLUS NET CP 1242-7 V2 (6AG1242-7KX31-7XE0) <V3.3.46 Siemens SIPLUS NET CP 1543-1 (6AG1543-1AX00-2XE0) <V3.0.22 Siemens SIPLUS S7-1200 CP 1243-1 (6AG1243-1BX30-2AX0) <V3.3.46
    affected: mitigation “Siemens has identified the following specific workarounds and mitigations users can apply to reduce risk:” support.industry.siemens.com

1 more affected in the full advisory

From CISA ICS and IT advisories (CSAF, https://github.com/cisagov/CSAF), a U.S. Government work; changed: reduced to products, statuses and remediations. CISA notification · csaf

Exploit prediction

5.30% chance of exploitation in the next 30 days, higher than 92% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P

Classification

Weakness
  • CWE-190 Integer Overflow or Wraparound

References

Sources

Fencer Intel 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.