Every CVESearch/Get API key

CVE-2026-77205

Denial of Service via sending bogus X.509 certificates

3.7 LowFix available

CVE-2026-77205 is a low vulnerability (CVSS 3.7) in The Libreswan Project Libreswan, published October 13, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.18%, the 7th percentile. Fixed in libreswan 5.3.3-r0.

Severity
3.7 LowCVSS 3.1, CVE List
Exploit chance
0.18%EPSS, 7th percentile
Exploitation
None knownNot on CISA’s or ENISA’s lists
Fixed in
5.3.3-r0libreswan +18 more

Description

Libreswan in FIPS mode has a vulnerability where badly formed received certificates are rejected, but not deleted from the NSS cache. As a result, any real certificates with the same serial number are rejected as well. This can be abused to lock out legitimate peers from connecting. The add_decoded_cert() function missed a call to CERT_DestroyCertificate() due to an incorrect fix for CVE-2026-14957. Sending bogus certificates with new serial numbers could prevent the real certificates with those serial numbers from connecting until the service has restarted.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
Low

Exploit likelihood

0.18%Unchanged since Oct 14, 2026
90%50%10%1%

Affected products

Affected packages

Affected packages
PackageAffectedFixed
libreswan
Alpine:v3.23
before 5.3.3-r0
5.3.3-r0
libreswan
Alpine:v3.24
before 5.3.3-r0
5.3.3-r0
libreswan
AlmaLinux:10
From an advisory covering 3 CVEs
before 5.3.3-1.el10_2
5.3.3-1.el10_2
libreswan-minimal
AlmaLinux:10
From an advisory covering 3 CVEs
before 5.3.3-1.el10_2
5.3.3-1.el10_2
libreswan
Debian:14
All versions, plus listed versions
5.2-2.25.2-2.35.2-2.45.2-2.5
None known
libreswan
Red Hat:enterprise_linux:10.2
From an advisory covering 3 CVEs
before 0:5.3.3-1.el10_2
0:5.3.3-1.el10_2
libreswan-debugsource
Red Hat:enterprise_linux:10.2
From an advisory covering 3 CVEs
before 0:5.3.3-1.el10_2
0:5.3.3-1.el10_2
libreswan-minimal
Red Hat:enterprise_linux:10.2
From an advisory covering 3 CVEs
before 0:5.3.3-1.el10_2
0:5.3.3-1.el10_2
libreswan-minimal-debuginfo
Red Hat:enterprise_linux:10.2
From an advisory covering 3 CVEs
before 0:5.3.3-1.el10_2
0:5.3.3-1.el10_2
libreswan
Red Hat:enterprise_linux:9::fastdatapath
From an advisory covering 4 CVEs
before 0:5.3.3-3.el9fdp
0:5.3.3-3.el9fdp
Show 9 moreShow less
Affected packages
PackageAffectedFixed
libreswan-debuginfo
Red Hat:enterprise_linux:9::fastdatapath
From an advisory covering 4 CVEs
before 0:5.3.3-3.el9fdp
0:5.3.3-3.el9fdp
libreswan-debugsource
Red Hat:enterprise_linux:9::fastdatapath
From an advisory covering 4 CVEs
before 0:5.3.3-3.el9fdp
0:5.3.3-3.el9fdp
libreswan
Rocky Linux:10
From an advisory covering 3 CVEs
before 0:5.3.3-1.el10_2
0:5.3.3-1.el10_2
libreswan
Ubuntu:18.04:LTS
All versions, plus listed versions
3.20-7build13.21-23.22-13.22-23.22-33.22-43.23-13.23-4
None known
libreswan
Ubuntu:20.04:LTS
All versions, plus listed versions
3.29-23.29-2build1
None known
libreswan
Ubuntu:22.04:LTS
All versions, plus listed versions
3.32-3ubuntu3
None known
libreswan
Ubuntu:24.04:LTS
All versions, plus listed versions
4.11-1ubuntu14.12-1ubuntu14.14-1ubuntu14.14-1ubuntu2
None known
libreswan
Ubuntu:26.10
All versions, plus listed versions
5.2-2.2ubuntu2
None known
libreswan
Ubuntu:26.04:LTS
All versions, plus listed versions
5.2-2.2ubuntu15.2-2.2ubuntu2
None known

What each source reports

CVE List Score used3.7

Denial of Service via sending bogus X.509 certificates

Libreswan in FIPS mode has a vulnerability where badly formed received certificates are rejected, but not deleted from the NSS cache. As a result, any real certificates with the same serial number are rejected as well. This can be abused to lock out legitimate peers from connecting. The add_decoded_cert() function missed a call to CERT_DestroyCertificate() due to an incorrect fix for CVE-2026-14957. Sending bogus certificates with new serial numbers could prevent the real certificates with those serial numbers from connecting until the service has restarted.

Record
CVE-2026-77205
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness
CWE-772
Updated
2026-11-02
EUVDEUVD-2026-1007473.7

Libreswan in FIPS mode has a vulnerability where badly formed received certificates are rejected, but not deleted from the NSS cache. As a result, any real certificates with the same serial number are rejected as well. This can be abused to lock out legitimate peers from connecting. The add_decoded_cert() function missed a call to CERT_DestroyCertificate() due to an incorrect fix for CVE-2026-14957. Sending bogus certificates with new serial numbers could prevent the real certificates with those serial numbers from connecting until the service has restarted.

Record
EUVD-2026-100747
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Updated
2026-11-02
GitHub AdvisoriesGHSA-7m29-c28j-rg7h3.7

Libreswan in FIPS mode has a vulnerability where badly formed received certificates are rejected,...

Libreswan in FIPS mode has a vulnerability where badly formed received certificates are rejected, but not deleted from the NSS cache. As a result, any real certificates with the same serial number are rejected as well. This can be abused to lock out legitimate peers from connecting. The add_decoded_cert() function missed a call to CERT_DestroyCertificate() due to an incorrect fix for CVE-2026-14957. Sending bogus certificates with new serial numbers could prevent the real certificates with those serial numbers from connecting until the service has restarted.

Record
GHSA-7m29-c28j-rg7h
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness
CWE-772
Updated
2026-11-02
NVD3.7

Libreswan in FIPS mode has a vulnerability where badly formed received certificates are rejected, but not deleted from the NSS cache. As a result, any real certificates with the same serial number are rejected as well. This can be abused to lock out legitimate peers from connecting. The add_decoded_cert() function missed a call to CERT_DestroyCertificate() due to an incorrect fix for CVE-2026-14957. Sending bogus certificates with new serial numbers could prevent the real certificates with those serial numbers from connecting until the service has restarted.

Record
CVE-2026-77205
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness
CWE-772
Updated
2026-11-02
OSVALPINE-CVE-2026-772053.7

Libreswan in FIPS mode has a vulnerability where badly formed received certificates are rejected, but not deleted from the NSS cache. As a result, any real certificates with the same serial number are rejected as well. This can be abused to lock out legitimate peers from connecting. The add_decoded_cert() function missed a call to CERT_DestroyCertificate() due to an incorrect fix for CVE-2026-14957. Sending bogus certificates with new serial numbers could prevent the real certificates with those serial numbers from connecting until the service has restarted.

Record
ALPINE-CVE-2026-77205
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Updated
2026-11-03
OSVDEBIAN-CVE-2026-772053.7

Libreswan in FIPS mode has a vulnerability where badly formed received certificates are rejected, but not deleted from the NSS cache. As a result, any real certificates with the same serial number are rejected as well. This can be abused to lock out legitimate peers from connecting. The add_decoded_cert() function missed a call to CERT_DestroyCertificate() due to an incorrect fix for CVE-2026-14957. Sending bogus certificates with new serial numbers could prevent the real certificates with those serial numbers from connecting until the service has restarted.

Record
DEBIAN-CVE-2026-77205
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Updated
2026-11-02
Show 5 moreShow less
OSVRHSA-2026:899237.5

Red Hat Security Advisory: libreswan security update

Record
RHSA-2026:89923
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-13
OSVRHSA-2026:980467.5

Red Hat Security Advisory: libreswan security, bug fix, and enhancement update

Record
RHSA-2026:98046
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-13
OSVRLSA-2026:899237.5

Important: libreswan security update

Libreswan is an implementation of IPsec and IKE for Linux. IPsec is the Internet Protocol Security and uses strong cryptography to provide both authentication and encryption services. These services allow you to build secure tunnels through untrusted networks such as virtual private network (VPN).

Security Fix(es):

  • libreswan: IKEv2 Use-After-Free bug when using IKE-over-TCP (CVE-2026-94453)

  • libreswan: Denial of Service via sending bogus X.509 certificates (CVE-2026-77205)

  • libreswan: Null Pointer Dereference in PKCS#7 bundle with no CERTS (CVE-2026-77207)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Record
RLSA-2026:89923
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2026-772053.7

Libreswan in FIPS mode has a vulnerability where badly formed received certificates are rejected, but not deleted from the NSS cache. As a result, any real certificates with the same serial number are rejected as well. This can be abused to lock out legitimate peers from connecting. The add_decoded_cert() function missed a call to CERT_DestroyCertificate() due to an incorrect fix for CVE-2026-14957. Sending bogus certificates with new serial numbers could prevent the real certificates with those serial numbers from connecting until the service has restarted.

Record
UBUNTU-CVE-2026-77205
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Updated
2026-11-02
OSVALSA-2026:89923No score

Important: libreswan security update

Libreswan is an implementation of IPsec and IKE for Linux. IPsec is the Internet Protocol Security and uses strong cryptography to provide both authentication and encryption services. These services allow you to build secure tunnels through untrusted networks such as virtual private network (VPN).

Security Fix(es):

  • libreswan: IKEv2 Use-After-Free bug when using IKE-over-TCP (CVE-2026-94453)
  • libreswan: Denial of Service via sending bogus X.509 certificates (CVE-2026-77205)
  • libreswan: Null Pointer Dereference in PKCS#7 bundle with no CERTS (CVE-2026-77207)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Record
ALSA-2026:89923
Updated
2026-11-02

History

History
RecordedChangedSources
affected, aliases, referencesOSV
affected, facts
affected, aliases, referencesOSV
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

References

Show 38 moreShow less
PagesAll vulnerabilitiesBrowseDocsSourcesGuideGet API key
MoveEnter Open