# CVE-2021-39275 — Apache HTTP Server > As of 2024-08-04, CVE-2021-39275 is a CRITICAL-severity vulnerability in Apache HTTP Server, CVSS v3.1 9.8, EPSS 39.4% (98.4th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2021-39275, most recently “Russian Intelligence Services Hijack Unsecured IP Cameras Across NATO, EU and Ukraine to Surveil Weapons Deliveries (AIVD/MIVD Advisory, Censys Analysis)”. **Last updated:** 2024-08-04 ## What is CVE-2021-39275? ap_escape_quotes() may write beyond the end of a buffer when given malicious input. No included modules pass untrusted data to these functions, but third-party / external modules may. This issue affects Apache HTTP Server 2.4.48 and earlier. The record classifies CVE-2021-39275 under weakness class [CWE-787](https://intel.threadlinqs.com/cwe/CWE-787). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 1845 days ago. ## Severity and exploitation probability - **CVSS v3.1 base score:** 9.8 — CRITICAL (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`) - **EPSS (FIRST):** 39.4% probability of exploitation in the next 30 days, higher than 98.4% of all scored CVEs - **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog - **Threadlinqs priority:** 10/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability - **Published:** 2021-09-16, last modified 2024-08-04 ## Is CVE-2021-39275 being exploited? Weaponised exploit code for CVE-2021-39275 is publicly available. 1 public proof-of-concept repository is tracked for this identifier. - [trickest/cve](https://github.com/trickest/cve/blob/main/2021/CVE-2021-39275.md) (trickest) ## Affected products and versions - [Apache Software Foundation](https://intel.threadlinqs.com/vendors/apache-software-foundation): Apache HTTP Server ## How to fix CVE-2021-39275 The record marks a vendor fix as available for CVE-2021-39275. Patch reference: [https://lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a143028bb32910432%40%3Cusers.httpd.apache.org%3E](https://lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a143028bb32910432%40%3Cusers.httpd.apache.org%3E). Vendor advisory: [https://httpd.apache.org/security/vulnerabilities_24.html](https://httpd.apache.org/security/vulnerabilities_24.html). Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory. ## Threat activity tracking CVE-2021-39275 1 tracked threat in the Threadlinqs corpus references CVE-2021-39275, either in the campaign’s CVE list or as an indicator on the campaign record. - [Russian Intelligence Services Hijack Unsecured IP Cameras Across NATO, EU and Ukraine to Surveil Weapons Deliveries (AIVD/MIVD Advisory, Censys Analysis)](https://intel.threadlinqs.com/threat/TL-2026-1624) — HIGH · 2026-07-22 ## Sources Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on 2026-08-17. This product uses the NVD API but is not endorsed or certified by the NVD. **Vendor advisory and patch** - [lists.fedoraproject.org — vendor advisory](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SPBR6WUYBJNACHKE65SPL7TJOHX7RHWD/) - [lists.fedoraproject.org — vendor advisory (ZNCYSR3BXT36FFF4XTCPL3HDQK4VP45R)](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNCYSR3BXT36FFF4XTCPL3HDQK4VP45R/) - [debian.org — vendor advisory](https://www.debian.org/security/2021/dsa-4982) - [tools.cisco.com — vendor advisory](https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ) - [security.netapp.com](https://security.netapp.com/advisory/ntap-20211008-0004/) **Mailing list and disclosure** - [lists.apache.org — mailing list](https://lists.apache.org/thread.html/r82838efc5fa6fc4c73986399c9b71573589f78b31846aff5bd9b1697%40%3Cusers.httpd.apache.org%3E) - [lists.apache.org — mailing list (r82c077663f9759c7df5a6656f925b3ee4f55fcd)](https://lists.apache.org/thread.html/r82c077663f9759c7df5a6656f925b3ee4f55fcd33c889ba7cd687029%40%3Cusers.httpd.apache.org%3E) - [lists.apache.org — mailing list (r3925e167d5eb1c75def3750c155d753064e1d34)](https://lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a143028bb32910432%40%3Cusers.httpd.apache.org%3E) - [lists.apache.org — mailing list (r61fdbfc26ab170f4e6492ef3bd5197c20b862ce)](https://lists.apache.org/thread.html/r61fdbfc26ab170f4e6492ef3bd5197c20b862ce156e9d5a54d4b899c%40%3Cusers.httpd.apache.org%3E) - [lists.debian.org — mailing list](https://lists.debian.org/debian-lts-announce/2021/10/msg00001.html) **Other references** - [httpd.apache.org](https://httpd.apache.org/security/vulnerabilities_24.html) - [oracle.com](https://www.oracle.com/security-alerts/cpujan2022.html) - [oracle.com (cpuapr2022)](https://www.oracle.com/security-alerts/cpuapr2022.html) _Showing 13 of 15 recorded references._ Canonical: https://intel.threadlinqs.com/cve/CVE-2021-39275 Full detection coverage and IOCs for threats exploiting CVE-2021-39275 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp