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Fencer Vulns
low 3.7

CVE-2026-77205 json

Denial of Service via sending bogus X.509 certificates

published 2026-10-13 26 d ago modified 2026-10-16 23 d ago also EUVD-2026-100747

cvss
3.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 7%
public exploits
0
none known

Summary

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.

Patch / fix

  • The Libreswan Project libreswan 5.3.3
  • libreswan AlmaLinux 10 5.3.3-1.el10_2
  • libreswan-minimal AlmaLinux 10 5.3.3-1.el10_2

almalinux advisories ALSA-2026:89923

  • libreswan Rocky Linux 10 5.3.3-1.el10_2

rocky linux advisories RLSA-2026:89923

  • libreswan Alpine 3.24, Alpine 3.23 5.3.3-r0

alpine advisories ALPINE-CVE-2026-77205

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

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-2026-77205 updated cvss 3.7

libreswan: Denial of Service via sending bogus X.509 certificates

  • Red Hat Fast Datapath for RHEL 9 libreswan Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available “Disabling FIPS mode will prevent this attack vector. However, disabling FIPS mode may violate security or compliance requirements and should not be used as a workaround without authorization.”
  • Red Hat Enterprise Linux AppStream (v. 10) libreswan 5.3.3-1.el10_2, libreswan-minimal 5.3.3-1.el10_2
    fixed: vendor fix “Disabling FIPS mode will prevent this attack vector. However, disabling FIPS mode may violate security or compliance requirements and should not be used as a workaround without authorization.” RHSA-2026:89923
  • Red Hat Enterprise Linux 6 libreswan Red Hat Enterprise Linux 7 libreswan Red Hat Enterprise Linux 8 libreswan Red Hat Enterprise Linux 9 libreswan Red Hat OpenShift Container Platform 4 libreswan
    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 SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
23 d ago

Exploit prediction

0.18% chance of exploitation in the next 30 days, higher than 7% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected products

  • The Libreswan Project libreswan

Classification

Weakness
  • CWE-772 Missing Release of Resource after Effective Lifetime

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.