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Fencer Vulns
medium 5.9

CVE-2021-32791 json

Hardcoded static IV and AAD with a reused key in AES GCM encryption in mod_auth_openidc

published 2021-07-26 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-19554

cvss
5.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.5%
EPSS 1.5% chance of exploitation in 30 days, percentile 74%
public exploits
0
none known

Summary

mod_auth_openidc is an authentication/authorization module for the Apache 2.x HTTP server that functions as an OpenID Connect Relying Party, authenticating users against an OpenID Connect Provider. In mod_auth_openidc before version 2.4.9, the AES GCM encryption in mod_auth_openidc uses a static IV and AAD. It is important to fix because this creates a static nonce and since aes-gcm is a stream cipher, this can lead to known cryptographic issues, since the same key is being reused. From 2.4.9 onwards this has been patched to use dynamic values through usage of cjose AES encryption routines.

Patch / fix

  • openidc mod_auth_openidc 2.4.9
  • libapache2-mod-auth-openidc Debian 14, Debian 13, Debian 12 2.4.9-1

debian advisories DEBIAN-CVE-2021-32791

  • cjose RHEL 8 0.6.1-2.module+el8+2454+f890a43a
  • mod_auth_openidc RHEL 8 2.3.7-11.module+el8.6.0+14082+b6f23e95

red hat advisories RHSA-2022:1823

  • apache2-mod_auth_openidc SLE Module for Server Applications 15 SP7, SLE Module for Server Applications 15 SP6, openSUSE Leap 15.6 2.4.17.1-150600.16.14.1
  • apache2-mod_auth_openidc SLES for SAP 12 SP5, SLES 12 SP5 2.4.0-3.23.1
  • apache2-mod_auth_openidc SLE Module for Server Applications 15 SP3, SLE Module for Server Applications 15 SP2 2.3.8-3.15.1

suse advisories SUSE-SU-2025:4532-1SUSE-SU-2021:3352-1SUSE-SU-2021:3020-1

  • apache2-mod_auth_openidc openSUSE Leap 15.2 2.3.8-lp152.5.6.1
  • apache2-mod_auth_openidc openSUSE Leap 15.3 2.3.8-3.15.1

opensuse advisories openSUSE-SU-2021:1277-1openSUSE-SU-2021:3020-1

  • cjose AlmaLinux 8 0.6.1-2.module_el8.6.0+2868+44838709
  • mod_auth_openidc AlmaLinux 8 2.3.7-11.module_el8.6.0+2868+44838709

almalinux advisories ALSA-2022:1823

  • cjose Rocky Linux 8 0.6.1-2.module+el8.3.0+129+2feafa46
  • mod_auth_openidc Rocky Linux 8 2.3.7-11.module+el8.6.0+840+73eca44e

rocky linux advisories RLSA-2022:1823

  • httpd CBL-Mariner 2.0 2.4.52-1

azure linux advisories AZL-6481

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-2021-32791 updated cvss 5.9

mod_auth_openidc: hardcoded static IV and AAD with a reused key in AES GCM encryption

  • Red Hat Enterprise Linux 7 mod_auth_openidc
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) cjose 0.6.1-2.module+el8+2454+f890a43a, mod_auth_openidc 2.3.7-11.module+el8.6.0+14082+b6f23e95
    fixed: vendor fix RHSA-2022:1823
  • Red Hat Enterprise Linux 9 mod_auth_openidc
    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

Exploit prediction

1.50% chance of exploitation in the next 30 days, higher than 74% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:P/I:N/A:N

Affected products

  • zmartzone mod_auth_openidc

Classification

Weakness
  • CWE-323 Reusing a Nonce, Key Pair in Encryption
  • CWE-330 Use of Insufficiently Random Values

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.