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NVD / CVE Program· CNA GitHub_M

CVE-2021-32785: Format string bug in the Redis cache implementation

Noroxi assessment

Priority: Monitor (action score 31/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 2.7% (FIRST EPSS); higher than 86.1% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: libapache2-mod-auth-openidc (Debian:10) 2.3.10.2-1+deb10u2; libapache2-mod-auth-openidc (Debian:12) 2.4.9-1; apache2-mod_auth_openidc (openSUSE:Leap 15.2) 2.3.8-lp152.5.6.1.
  • Severity is disputed: the assigning authority (CNA) scores it 5.3, NVD 7.5.

Low priority for now. Upgrade to libapache2-mod-auth-openidc (Debian:10) 2.3.10.2-1+deb10u2; libapache2-mod-auth-openidc (Debian:12) 2.4.9-1; apache2-mod_auth_openidc (openSUSE:Leap 15.2) 2.3.8-lp152.5.6.1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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. When mod_auth_openidc versions prior to 2.4.9 are configured to use an unencrypted Redis cache (`OIDCCacheEncrypt off`, `OIDCSessionType server-cache`, `OIDCCacheType redis`), `mod_auth_openidc` wrongly performed argument interpolation before passing Redis requests to `hiredis`, which would perform it again and lead to an uncontrolled format string bug. Initial assessment shows that this bug does not appear to allow gaining arbitrary code execution, but can reliably provoke a denial of service by repeatedly crashing the Apache workers. This bug has been corrected in version 2.4.9 by performing argument interpolation only once, using the `hiredis` API. As a workaround, this vulnerability can be mitigated by setting `OIDCCacheEncrypt` to `on`, as cache keys are cryptographically hashed before use when this option is enabled.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Jul 22, 2021
Updated
Jun 16, 2026
EPSS
2.7% · 86th percentile

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 2.7%

CNA vs NVD score

NVD
7.5
CNA · GitHub_M
5.3
2.2 point gap

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-32785

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
openidcmod auth openidc
apachehttp server
netappcloud backup
debiandebian linux

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux10.0
  • netapp cloud backupall versions
  • openidc mod auth openidcbefore 2.4.9

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • zmartzone mod_auth_openidc

    • < 2.4.9affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:10libapache2-mod-auth-openidcbefore 2.3.10.2-1+deb10u22.3.10.2-1+deb10u2
Debian:12libapache2-mod-auth-openidcbefore 2.4.9-12.4.9-1
openSUSE:Leap 15.2apache2-mod_auth_openidcbefore 2.3.8-lp152.5.6.12.3.8-lp152.5.6.1
openSUSE:Leap 15.3apache2-mod_auth_openidcbefore 2.3.8-3.15.12.3.8-3.15.1
openSUSE:Leap 15.6apache2-mod_auth_openidcbefore 2.4.17.1-150600.16.14.12.4.17.1-150600.16.14.1
openSUSE:Tumbleweedapache2-mod_auth_openidcbefore 2.4.9.4-1.22.4.9.4-1.2
SUSE:Linux Enterprise Module for Server Applications 15 SP2apache2-mod_auth_openidcbefore 2.3.8-3.15.12.3.8-3.15.1
SUSE:Linux Enterprise Module for Server Applications 15 SP6apache2-mod_auth_openidcbefore 2.4.17.1-150600.16.14.12.4.17.1-150600.16.14.1
SUSE:Linux Enterprise Server 12 SP5apache2-mod_auth_openidcbefore 2.4.0-3.23.12.4.0-3.23.1

Same product

openidc: all records

Other highest-scoring records for the same primary product.

  • CVE-2017-6413The "OpenID Connect Relying Party and OAuth 2.0 Resource Server" (aka mod_auth_openidc) module before 2.1.6 for the Apache HTTP Server does
    35Monitor
  • CVE-2017-6062The "OpenID Connect Relying Party and OAuth 2.0 Resource Server" (aka mod_auth_openidc) module before 2.1.5 for the Apache HTTP Server does
    35Monitor
  • CVE-2017-6059Mod_auth_openidc.c in the Ping Identity OpenID Connect authentication module for Apache (aka mod_auth_openidc) before 2.14 allows remote att
    32Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2019-20479Feb 20, 2020 · A flaw was found in mod_auth_openidc before version 2.4.1.
    25Monitor
  • ← EarlierCVE-2021-20718May 19, 2021 · mod_auth_openidc 2.4.0 to 2.4.7 allows a remote attacker to cause a denial-of-service (DoS) condition via unspecified vectors.
    31Monitor
  • Later →CVE-2021-32786Jul 22, 2021 · Open Redirect in oidc_validate_redirect_url()
    25Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:libapache2-mod-auth-openidc2.4.9-1 · Debian:12Package registry (OSV)
opensuse:apache2-mod_auth_openidc2.4.17.1-150600.16.14.1 · openSUSE:Leap 15.6Package registry (OSV)
suse:apache2-mod_auth_openidc2.3.8-3.15.1 · SUSE:Linux Enterprise Module for Server Applications 15 SP2Package registry (OSV)
suse:apache2-mod_auth_openidc2.4.17.1-150600.16.14.1 · SUSE:Linux Enterprise Module for Server Applications 15 SP6Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-134 · Use of Externally-Controlled Format String

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records