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Fencer Vulns
high 8.7

CVE-2026-63383 json

Libevent: decode_tag_internal() can lead to out-of-bounds read

published 2026-08-20 2 mo ago modified 2026-10-26 14 d ago also EUVD-2026-63502

cvss
8.7
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits
0
none known

Summary

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent can read beyond a contiguous evbuffer region in event_tagging.c when decode_tag_internal requests at most five bytes from evbuffer_pullup but iterates using the full logical buffer length. A fragmented evbuffer containing a six-byte malformed tag can therefore advance past the pullup window and trigger an out-of-bounds read, which can crash a process that decodes attacker-controlled tagged RPC data. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

Patch / fix

  • libevent_project libevent 2.1.13, 2.2.2-alpha
  • libevent Debian 12 2.1.12-stable-8+deb12u1
  • libevent Debian 13 2.1.13-stable-1~deb13u1
  • libevent Debian 14 2.1.13-stable-1

debian advisories DEBIAN-CVE-2026-63383

  • libevent Ubuntu 22.04 LTS 2.1.12-stable-1ubuntu0.1
  • libevent Ubuntu 24.04 LTS 2.1.12-stable-9ubuntu2.1
  • libevent Ubuntu 26.04 LTS 2.1.12-stable-10ubuntu0.1
  • libevent Ubuntu Pro 14.04 LTS 2.0.21-stable-1ubuntu1.14.04.2+esm1
  • libevent Ubuntu Pro 16.04 LTS 2.0.21-stable-2ubuntu0.16.04.1+esm1
  • libevent Ubuntu Pro 18.04 LTS 2.1.8-stable-4ubuntu0.1~esm1
  • libevent Ubuntu Pro 20.04 LTS 2.1.11-stable-1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2026-63383

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

  • libevent RHEL 9 2.1.13-1.el9_8
  • libevent RHEL 8 2.1.8-11.el8_10
  • libevent RHEL 10.2 2.1.13-1.el10_2
  • libevent hummingbird 1 2.1.12-19.1.hum1

red hat advisories RHSA-2026:67910RHSA-2026:67908RHSA-2026:67909RHSA-2026:60853

  • libevent openSUSE Tumbleweed 2.1.13-1.1

opensuse advisories openSUSE-SU-2026:12330-1

  • libevent AlmaLinux 8 2.1.8-11.el8_10
  • libevent AlmaLinux 10 2.1.13-1.el10_2
  • libevent AlmaLinux 9 2.1.13-1.el9_8

almalinux advisories ALSA-2026:67908ALSA-2026:67909ALSA-2026:67910

  • libevent Rocky Linux 10 2.1.13-1.el10_2
  • libevent Rocky Linux 8 2.1.8-11.el8_10
  • libevent Rocky Linux 9 2.1.13-1.el9_8

rocky linux advisories RLSA-2026:67909RLSA-2026:67908RLSA-2026:67910

  • libevent Azure Linux 3.0 2.1.13-1
  • mysql Azure Linux 3.0 8.0.46-2
  • ntp Azure Linux 3.0 4.2.8p17-3

azure linux advisories AZL-96938AZL-97521AZL-97551

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

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-2026-63383 updated cvss 7.5

libevent: Libevent: Denial of Service via malformed RPC data

  • Red Hat Enterprise Linux 6 libevent 1.4.13-4.el6, libevent2 2.0.21-2.el6
    affected: workaround, no fix available, no fix planned “Will not fix”
  • Red Hat Enterprise Linux 7 libevent 1.4.13-4.el6 Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.20 cert-manager/cert-manager-operator-rhel9 1790272426, cert-manager/cert-manager-operator-rhel9 1790589855, cert-manager/jetstack-cert-manager-rhel9 1790223279, cert-manager/jetstack-cert-manager-rhel9 1790589912, cert-manager/cert-manager-istio-csr-rhel9 1790223719, cert-manager/cert-manager-istio-csr-rhel9 1790589914, +1 more
    fixed: vendor fix RHSA-2026:72475
  • Red Hat Enterprise Linux AppStream (v. 8) libevent-devel 2.1.8-11.el8_10, libevent-debuginfo 2.1.8-11.el8_10, libevent-debugsource 2.1.8-11.el8_10
    fixed: vendor fix RHSA-2026:67908
  • Red Hat Enterprise Linux AppStream (v. 9) libevent-doc 2.1.13-1.el9_8, libevent-devel 2.1.13-1.el9_8, libevent-debuginfo 2.1.13-1.el9_8, libevent-debugsource 2.1.13-1.el9_8
    fixed: vendor fix RHSA-2026:67910
  • Red Hat Enterprise Linux AppStream (v. 10) libevent-doc 2.1.13-1.el10_2, libevent-devel 2.1.13-1.el10_2, libevent-debuginfo 2.1.13-1.el10_2, libevent-debugsource 2.1.13-1.el10_2
    fixed: vendor fix RHSA-2026:67909
  • Red Hat Enterprise Linux BaseOS (v. 8) libevent 2.1.8-11.el8_10
    fixed: vendor fix RHSA-2026:67908
  • Red Hat Enterprise Linux BaseOS (v. 9) libevent 2.1.13-1.el9_8
    fixed: vendor fix RHSA-2026:67910
show 5 more
  • Red Hat Enterprise Linux BaseOS (v. 10) libevent 2.1.13-1.el10_2
    fixed: vendor fix RHSA-2026:67909
  • Red Hat Hardened Images libevent 2.1.12-19.1.hum1
    fixed: vendor fix RHSA-2026:60853
  • Red Hat OpenShift Container Platform 4.22 rhcos 4.22.9.8.202610241758
    fixed: vendor fix RHSA-2026:89197
  • Red Hat Update Infrastructure 5 rhui5/cds-rhel9 1790241954, rhui5/rhua-rhel9 1790242004, rhui5/haproxy-rhel9 1790241900, rhui5/installer-rhel9 1790241922, rhui5/cds-kubernetes-rhel9 1790241897
    fixed: vendor fix RHSA-2026:71603
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.20 cert-manager/jetstack-cert-manager-acmesolver-rhel9 1790223630 Red Hat OpenShift AI (RHOAI) rhoai/odh-llama-stack-k8s-operator-rhel9
    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
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
2 mo ago

Exploit prediction

0.49% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/libevent/libevent/security/advisories/GHSA-fj29-64w6-73h6 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • libevent libevent

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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.