CVE-2020-35452

CVE-2020-35452 is a high-severity vulnerability in Apache Http Server with a CVSS 3.x base score of 7.3. Its EPSS exploit-prediction score of 53% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-787.

Key facts

• Severity: High (CVSS 3.x base score 7.3)
• CVSS v2: 6.8
• EPSS exploit prediction: 53% (99th percentile)
• Actively exploited: Not listed in CISA KEV
• Weakness: CWE-787
• Affected product: Apache Http Server
• Published: 2021-06-10
• Last modified: 2026-06-17

Description

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

Frequently asked questions

What is CVE-2020-35452?

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

How severe is CVE-2020-35452?

CVE-2020-35452 has a CVSS 3.x base score of 7.3, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.

Is CVE-2020-35452 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 53% (99th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-35452?

CVE-2020-35452 primarily affects Apache Http Server. In total, 10 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-35452?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2020-35452 published?

CVE-2020-35452 was published on 2021-06-10 and last updated on 2026-06-17.

References

• http://httpd.apache.org/security/vulnerabilities_24.html
• http://www.openwall.com/lists/oss-security/2021/06/10/5
• https://lists.apache.org/thread.html/r7f2b70b621651548f4b6f027552f1dd91705d7111bb5d15cda0a68dd%40%3Cdev.httpd.apache.org%3E
• https://lists.apache.org/thread.html/rccb1b8225583a48c6360edc7a93cc97ae8b0215791e455dc607e7602%40%3Cannounce.httpd.apache.org%3E
• https://lists.apache.org/thread.html/re026d3da9d7824bd93b9f871c0fdda978d960c7e62d8c43cba8d0bf3%40%3Ccvs.httpd.apache.org%3E
• https://lists.debian.org/debian-lts-announce/2021/07/msg00006.html
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SPBR6WUYBJNACHKE65SPL7TJOHX7RHWD/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNCYSR3BXT36FFF4XTCPL3HDQK4VP45R/
• https://security.gentoo.org/glsa/202107-38
• https://security.netapp.com/advisory/ntap-20210702-0001/
• https://www.debian.org/security/2021/dsa-4937
• https://www.oracle.com/security-alerts/cpuoct2021.html

Affected products (10)

• cpe:2.3:a:apache:http_server:*:*:*:*:*:*:*:*
• cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
• cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
• cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
• cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:enterprise_manager_ops_center:12.4.0.0:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:instantis_enterprisetrack:17.1:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:instantis_enterprisetrack:17.2:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:instantis_enterprisetrack:17.3:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:zfs_storage_appliance_kit:8.8:*:*:*:*:*:*:*

More vulnerabilities in Apache Http Server

• CVE-2010-0425 — Critical (CVSS 10.0): modules/arch/win32/mod_isapi.c in mod_isapi in the Apache HTTP Server 2.0.37 through 2.0.63, 2.2.0 through 2.2.14, and…
• CVE-2005-2700 — Critical (CVSS 10.0): ssl_engine_kernel.c in mod_ssl before 2.8.24, when using "SSLVerifyClient optional" in the global virtual host…
• CVE-2004-0492 — Critical (CVSS 10.0): Heap-based buffer overflow in proxy_util.c for mod_proxy in Apache 1.3.25 to 1.3.31 allows remote attackers to cause a…
• CVE-2003-0789 — Critical (CVSS 10.0): mod_cgid in Apache before 2.0.48, when using a threaded MPM, does not properly handle CGI redirect paths, which could…
• CVE-1999-1293 — Critical (CVSS 10.0): mod_proxy in Apache 1.2.5 and earlier allows remote attackers to cause a denial of service via malformed FTP commands,…
• CVE-1999-0926 — Critical (CVSS 10.0): Apache allows remote attackers to conduct a denial of service via a large number of MIME headers.

All CVEs affecting Apache Http Server →

Other CWE-787 (Out-of-bounds Write) vulnerabilities

• CVE-2026-42369 — Critical (CVSS 10.0): GV-VMS V20 is a Video Monitoring Software used to gather the feeds of many surveillance cameras and manage other…
• CVE-2026-4746 — Critical (CVSS 10.0): Out-of-bounds Write vulnerability in timeplus-io proton (base/poco/Foundation/src‎ modules). This vulnerability is…
• CVE-2025-43300 — Critical (CVSS 10.0): An out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in iOS 15.8.5 and iPadOS…
• CVE-2025-24201 — Critical (CVSS 10.0): An out-of-bounds write issue was addressed with improved checks to prevent unauthorized actions. This issue is fixed in…
• CVE-2024-42479 — Critical (CVSS 10.0): llama.cpp provides LLM inference in C/C++. The unsafe `data` pointer member in the `rpc_tensor` structure can cause…
• CVE-2024-39791 — Critical (CVSS 10.0): Stack-based buffer overflow vulnerabilities affecting Vonets industrial wifi bridge relays and wifi bridge…

Browse all CWE-787 (Out-of-bounds Write) vulnerabilities →

Threat intelligence

Threat-intel indicators referencing this CVE:

• 50.255.62.89 (ipv4-addr)
• 147.15.15.226 (ipv4-addr)
• 45.84.120.3 (ipv4-addr)
• 61.76.112.4 (ipv4-addr)
• 60.199.224.2 (ipv4-addr)
• 46.253.45.10 (ipv4-addr)
• 45.232.73.84 (ipv4-addr)
• 45.120.115.150 (ipv4-addr)