CVE-2026-77205
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.
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
What each source reports
CVE List Score used
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 Low
CVSS: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-2026-100747
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 Low
CVSS: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-rg7h
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 Low
CVSS: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
NVD
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 Low
CVSS: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-2026-77205
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 Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L - Updated
- 2026-11-03
OSVDEBIAN-CVE-2026-77205
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 Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L - Updated
- 2026-11-02
OSVRLSA-2026:89923
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 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-77205
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 Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L - Updated
- 2026-11-02
OSVALSA-2026:89923 No 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
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
libreswanAlpine:v3.23 |
before 5.3.3-r0 | 5.3.3-r0 |
libreswanAlpine:v3.24 |
before 5.3.3-r0 | 5.3.3-r0 |
libreswanAlmaLinux:10 |
before 5.3.3-1.el10_2 | 5.3.3-1.el10_2 |
libreswan-minimalAlmaLinux:10 |
before 5.3.3-1.el10_2 | 5.3.3-1.el10_2 |
libreswanDebian:14 |
All versions, plus listed versions 5.2-2.25.2-2.35.2-2.45.2-2.5 |
None known |
libreswanRocky Linux:10 |
before 0:5.3.3-1.el10_2 | 0:5.3.3-1.el10_2 |
libreswanUbuntu: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 |
libreswanUbuntu:20.04:LTS |
All versions, plus listed versions 3.29-23.29-2build1 |
None known |
libreswanUbuntu:22.04:LTS |
All versions, plus listed versions 3.32-3ubuntu3 |
None known |
libreswanUbuntu:24.04:LTS |
All versions, plus listed versions 4.11-1ubuntu14.12-1ubuntu14.14-1ubuntu14.14-1ubuntu2 |
None known |
libreswanUbuntu:26.10 |
All versions, plus listed versions 5.2-2.2ubuntu2 |
None known |
libreswanUbuntu:26.04:LTS |
All versions, plus listed versions 5.2-2.2ubuntu15.2-2.2ubuntu2 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, aliases, references | OSV | |
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
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.
References
libreswan.org/security/CVE-2026-77205/CVE-2026-77205.txt
nvd.nist.gov/vuln/detail/CVE-2026-77205
github.com/advisories/GHSA-7m29-c28j-rg7h
security.alpinelinux.org/vuln/CVE-2026-77205
Show 15 moreShow less
access.redhat.com/errata/RHSA-2026:89923
bugzilla.redhat.com/2550254
errata.almalinux.org/10/ALSA-2026-89923.html
security-tracker.debian.org/tracker/CVE-2026-77205
errata.rockylinux.org/RLSA-2026:89923
ubuntu.com/security/CVE-2026-77205
cve.org/CVERecord?id=CVE-2026-77205