NVD / CVE Program· CNA apache

CVE-2020-35452: mod_auth_digest possible stack overflow by one nul byte

Noroxi assessment

Priority: Plan (action score 45/100)

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: 53.1% (FIRST EPSS); higher than 98.9% 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: httpd (AlmaLinux:8) 2.4.37-47.module_el8.6.0+2935+fb177b09.2, 2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma; httpd-devel (AlmaLinux:8) 2.4.37-47.module_el8.6.0+2935+fb177b09.2, 2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma; httpd-filesystem (AlmaLinux:8) 2.4.37-47.module_el8.6.0+2935+fb177b09.2, 2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma.
Mentioned 3 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Add it to your regular patch cycle. Upgrade to httpd (AlmaLinux:8) 2.4.37-47.module_el8.6.0+2935+fb177b09.2, 2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma; httpd-devel (AlmaLinux:8) 2.4.37-47.module_el8.6.0+2935+fb177b09.2, 2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma; httpd-filesystem (AlmaLinux:8) 2.4.37-47.module_el8.6.0+2935+fb177b09.2, 2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma 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

Apache HTTP Server versions 2.4.0 to 2.4.46 A specially crafted Digest nonce can cause a stack overflow in mod_auth_digest. There is no report of this overflow being exploitable, nor the Apache HTTP Server team could create one, though some particular compiler and/or compilation option might make it possible, with limited consequences anyway due to the size (a single byte) and the value (zero byte) of the overflow

HighCVSS 7.3 · v3.1—No exploit Fix available

Published: Jun 10, 2021
Updated: Jun 16, 2026
EPSS: 53.1% · 98th percentile
CWE: CWE-787

Report tools

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Action score

Plan

Add it to your regular patch cycle.

CVSS: 29 / 40 · 7.3 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 16 / 30 · 53.1%

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

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Noroxi analysis

What does it mean in your environment?

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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.

Vendor	Product	CPE
apache	http server	cpe:2.3:a:apache:http_server
debian	debian linux	cpe:2.3:o:debian:debian_linux
fedoraproject	fedora	cpe:2.3:o:fedoraproject:fedora
oracle	enterprise manager ops center	cpe:2.3:a:oracle:enterprise_manager_ops_center
oracle	instantis enterprisetrack	cpe:2.3:a:oracle:instantis_enterprisetrack
oracle	zfs storage appliance kit	cpe:2.3:a:oracle:zfs_storage_appliance_kit

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Affected versions

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

apache http server2.4.0 and later · up to 2.4.46 inclusive

Versions reported by the vendor

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

Apache Software Foundation Apache HTTP Server
- 2.4.46, 2.4.43, 2.4.41, 2.4.39, 2.4.38, 2.4.37, 2.4.35, 2.4.34, 2.4.33, 2.4.29, 2.4.28, 2.4.27 … (+17)affected

Package-level exposure

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

+96

Same product

apache: all records

Other highest-scoring records for the same primary product.

CVE-2021-42013Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773)KEV
99Now
CVE-2021-41773Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49KEV
99Now
CVE-2024-38475Apache HTTP Server weakness in mod_rewrite when first segment of substitution matches filesystem path.KEV
96Now

Published before and after this one in the same product

← EarlierCVE-2020-13938Jun 10, 2021 · Improper Handling of Insufficient Privileges
26Monitor
← EarlierCVE-2020-13950Jun 10, 2021 · mod_proxy_http NULL pointer dereference
45Plan
Later →CVE-2021-26690Jun 10, 2021 · mod_session NULL pointer dereference
50Plan

Remediation

Which version to upgrade to

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

Product / package	Fixed version	Source
almalinux:httpd	2.4.37-47.module_el8.6.0+2935+fb177b09.2 · AlmaLinux:8	Package registry (OSV)
almalinux:httpd-devel	2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma · AlmaLinux:8	Package registry (OSV)
almalinux:httpd-filesystem	2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma · AlmaLinux:8	Package registry (OSV)
almalinux:httpd-manual	2.4.37-47.module_el8.6.0+2935+fb177b09.2 · AlmaLinux:8	Package registry (OSV)
almalinux:httpd-tools	2.4.37-47.module_el8.6.0+2935+fb177b09.2 · AlmaLinux:8	Package registry (OSV)
almalinux:mod_http2	1.15.7-5.module_el8.6.0+2872+fe0ff7aa · AlmaLinux:8	Package registry (OSV)
almalinux:mod_ldap	2.4.37-47.module_el8.6.0+2935+fb177b09.2 · AlmaLinux:8	Package registry (OSV)
almalinux:mod_md	1:2.0.8-8.module_el8.6.0+2872+fe0ff7aa · AlmaLinux:8	Package registry (OSV)
almalinux:mod_proxy_html	1:2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma · AlmaLinux:8	Package registry (OSV)
almalinux:mod_session	2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma · AlmaLinux:8	Package registry (OSV)
almalinux:mod_ssl	1:2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma · AlmaLinux:8	Package registry (OSV)
alpine:apache2	2.4.48-r0 · Alpine:v3.10	Package registry (OSV)
debian:apache2	2.4.46-6 · Debian:12	Package registry (OSV)
opensuse:apache2	2.4.43-lp152.2.15.1 · openSUSE:Leap 15.2	Package registry (OSV)
red hat:jbcs-httpd24-apr	0:1.6.3-107.jbcs.el7 · Red Hat:jboss_core_services:1::el7	Package registry (OSV)
red hat:jbcs-httpd24-apr-debuginfo	0:1.6.3-107.jbcs.el7 · Red Hat:jboss_core_services:1::el7	Package registry (OSV)
red hat:jbcs-httpd24-apr-devel	0:1.6.3-107.jbcs.el7 · Red Hat:jboss_core_services:1::el7	Package registry (OSV)
red hat:jbcs-httpd24-apr-util	0:1.6.1-84.jbcs.el7 · Red Hat:jboss_core_services:1::el7	Package registry (OSV)
red hat:jbcs-httpd24-apr-util-debuginfo	0:1.6.1-84.jbcs.el7 · Red Hat:jboss_core_services:1::el7	Package registry (OSV)
red hat:jbcs-httpd24-apr-util-devel	0:1.6.1-84.jbcs.el7 · Red Hat:jboss_core_services:1::el7	Package registry (OSV)
red hat:jbcs-httpd24-apr-util-ldap	0:1.6.1-84.jbcs.el7 · Red Hat:jboss_core_services:1::el7	Package registry (OSV)
red hat:jbcs-httpd24-apr-util-mysql	0:1.6.1-84.jbcs.el7 · Red Hat:jboss_core_services:1::el7	Package registry (OSV)
red hat:jbcs-httpd24-apr-util-nss	0:1.6.1-84.jbcs.el7 · Red Hat:jboss_core_services:1::el7	Package registry (OSV)
red hat:jbcs-httpd24-apr-util-odbc	0:1.6.1-84.jbcs.el7 · Red Hat:jboss_core_services:1::el7	Package registry (OSV)
red hat:jbcs-httpd24-apr-util-openssl	0:1.6.1-84.jbcs.el7 · Red Hat:jboss_core_services:1::el7	Package registry (OSV)
red hat:jbcs-httpd24-apr-util-pgsql	0:1.6.1-84.jbcs.el7 · Red Hat:jboss_core_services:1::el7	Package registry (OSV)
rocky linux:httpd	0:2.4.37-47.module+el8.6.0+823+f143cee1.1 · Rocky Linux:8	Package registry (OSV)
rocky linux:mod_http2	0:1.15.7-5.module+el8.6.0+823+f143cee1 · Rocky Linux:8	Package registry (OSV)
rocky linux:mod_md	1:2.0.8-8.module+el8.5.0+695+1fa8055e · Rocky Linux:8	Package registry (OSV)
suse:apache2	2.2.34-70.35.1 · SUSE:Linux Enterprise Point of Sale 11 SP3	Package 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.

EPSS, last 120 days-2% in 7 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

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

No commit or PR link among the references.

Credits

All researchers

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

GHSL team member @antonio-morales (Antonio Morales)

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).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

TR-21-0565 · Jul 12, 2021(Debian Güvenlik Güncellemesi Yayınladı)
TR-21-0505 · Jun 22, 2021(Apache Güvenlik Zafiyeti)
TR-21-0470 · Jun 11, 2021(Apache Güvenlik Zafiyeti)

All national notices →

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: low · data can be read
Integrity: low · data or configuration can be modified
Availability: low · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: Low
Integrity impact: Low
Availability impact: Low

Weakness class (CWE)

CWE-787 · Out-of-bounds Write

CVSS vector

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

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.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

Fix✗ → ✓Sep 28, 2026, 10:45 PM UTC

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

References

httpd.apache.org/security/vulnerabilities_24.html

Show all references (11 more)

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

All records