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Fencer Intel
critical 9.8

CVE-2021-39275 in the critical feed json

ap_escape_quotes buffer overflow

published 5y ago modified 24d ago also BIT-apache-2021-39275 , EUVD-2021-25637

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
39.4%
EPSS 39.4% chance of exploitation in 30 days, percentile 98%
public exploits
0
none known

Summary

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.

Patch / fix

  • bitnami apache 2.4.49
  • apache http_server 2.4.49
  • apache2 Debian 14, Debian 13, Debian 12 2.4.49-1

debian advisories DEBIAN-CVE-2021-39275

  • apache2 Ubuntu 18.04 LTS 2.4.29-1ubuntu4.17
  • apache2 Ubuntu 20.04 LTS 2.4.41-4ubuntu3.5
  • apache2 Ubuntu Pro 14.04 LTS 2.4.7-1ubuntu4.22+esm2
  • apache2 Ubuntu Pro 16.04 LTS 2.4.18-2ubuntu3.17+esm2

ubuntu advisories UBUNTU-CVE-2021-39275

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • httpd24-httpd RHEL 3 SOFTWARE_COLLECTIONS 2.4.34-23.el7.5
  • httpd24-mod_ssl RHEL 3 SOFTWARE_COLLECTIONS 1:2.4.34-23.el7.5
  • httpd24-mod_ldap RHEL 3 SOFTWARE_COLLECTIONS 2.4.34-23.el7.5
  • httpd24-httpd-tools RHEL 3 SOFTWARE_COLLECTIONS 2.4.34-23.el7.5
  • httpd24-mod_session RHEL 3 SOFTWARE_COLLECTIONS 2.4.34-23.el7.5
  • httpd24-httpd-manual RHEL 3 SOFTWARE_COLLECTIONS 2.4.34-23.el7.5
  • httpd24-mod_proxy_html RHEL 3 SOFTWARE_COLLECTIONS 1:2.4.34-23.el7.5
  • jbcs-httpd24-httpd jboss core services 1 2.4.51-28.el7jbcs

red hat advisories RHSA-2022:6753RHSA-2022:7143RHSA-2022:0143RHSA-2022:0891

  • apache2 SLE Module for Server Applications 15 SP3, SLE Module for Server Applications 15 SP2, SLE Module for Package Hub 15 SP3 +2 more 2.4.43-3.32.1
  • apache2 SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +7 more 2.4.33-3.55.1
  • apache2 SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +11 more 2.4.23-29.80.1
  • apache2 SLES 11 SP4-LTSS, SLE Point of Sale 11 SP3 2.2.34-70.38.1

suse advisories SUSE-SU-2021:3522-1SUSE-SU-2021:3335-1SUSE-SU-2021:3299-1SUSE-SU-2021:14811-1

  • apache2 openSUSE Leap 15.2 2.4.43-lp152.2.21.1
  • apache2 openSUSE Leap 15.3 2.4.43-3.32.1

opensuse advisories openSUSE-SU-2021:1438-1openSUSE-SU-2021:3522-1

  • httpd AlmaLinux 8 2.4.37-43.module_el8.5.0+2630+51c6d843.2.alma
  • mod_md AlmaLinux 8 1:2.0.8-8.module_el8.6.0+2872+fe0ff7aa
  • mod_ssl AlmaLinux 8 1:2.4.37-43.module_el8.5.0+2630+51c6d843.2.alma
  • mod_ldap AlmaLinux 8 2.4.37-43.module_el8.5.0+2630+51c6d843.2.alma
  • httpd-tools AlmaLinux 8 2.4.37-43.module_el8.5.0+2630+51c6d843.2.alma
  • mod_session AlmaLinux 8 2.4.37-43.module_el8.5.0+2630+51c6d843.2.alma
  • httpd-manual AlmaLinux 8 2.4.37-43.module_el8.5.0+2630+51c6d843.2.alma
  • mod_proxy_html AlmaLinux 8 1:2.4.37-43.module_el8.5.0+2630+51c6d843.2.alma

almalinux advisories ALSA-2022:0891

  • httpd Rocky Linux 8 2.4.37-43.module+el8.5.0+714+5ec56ee8
  • mod_md Rocky Linux 8 1:2.0.8-8.module+el8.5.0+695+1fa8055e
  • mod_md Rocky Linux 8 1:2.0.8-8.module+el8.4.0+553+7a69454b
  • mod_http2 Rocky Linux 8 1.15.7-3.module+el8.4.0+553+7a69454b
  • mod_http2 Rocky Linux 8 1.15.7-3.module+el8.5.0+695+1fa8055e

rocky linux advisories RLSA-2022:0891

  • apache2 Alpine 3.24, Alpine 3.23, Alpine 3.22 +11 more 2.4.49-r0

alpine advisories ALPINE-CVE-2021-39275

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • httpd CBL-Mariner 2.0 2.4.52-1

azure linux advisories AZL-6486

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

  • apache Arch Linux 2.4.49-1

arch linux advisories AVG-2289

Is CVE-2021-39275 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2021-39275 updated cvss 8.1

httpd: Out-of-bounds write in ap_escape_quotes() via malicious input

  • Red Hat Enterprise Linux 6 httpd, mod_ssl, httpd-tools, httpd-manual Red Hat JBoss Enterprise Application Platform 6 httpd, mod_ssl, mod_ldap, httpd-tools, httpd-manual
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) mod_md 2.0.8-8.module+el8.3.0+6814+67d1e611, httpd 2.4.37-43.module+el8.5.0+14370+51c6d843.2, mod_http2 1.15.7-3.module+el8.4.0+8625+d397f3da, mod_ssl 2.4.37-43.module+el8.5.0+14370+51c6d843.2, mod_ldap 2.4.37-43.module+el8.5.0+14370+51c6d843.2, httpd-tools 2.4.37-43.module+el8.5.0+14370+51c6d843.2, +4 more
    fixed: vendor fix RHSA-2022:0891
  • Red Hat Enterprise Linux Client Optional (v. 7) httpd 2.4.6-97.el7_9.4, mod_ssl 2.4.6-97.el7_9.4, mod_ldap 2.4.6-97.el7_9.4, httpd-tools 2.4.6-97.el7_9.4, mod_session 2.4.6-97.el7_9.4, httpd-manual 2.4.6-97.el7_9.4, +1 more Red Hat Enterprise Linux ComputeNode Optional (v. 7) httpd 2.4.6-97.el7_9.4, mod_ssl 2.4.6-97.el7_9.4, mod_ldap 2.4.6-97.el7_9.4, httpd-tools 2.4.6-97.el7_9.4, mod_session 2.4.6-97.el7_9.4, httpd-manual 2.4.6-97.el7_9.4, +1 more Red Hat Enterprise Linux Server (v. 7) httpd 2.4.6-97.el7_9.4, mod_ssl 2.4.6-97.el7_9.4, httpd-tools 2.4.6-97.el7_9.4, mod_session 2.4.6-97.el7_9.4, httpd-manual 2.4.6-97.el7_9.4 Red Hat Enterprise Linux Server Optional (v. 7) mod_ldap 2.4.6-97.el7_9.4, mod_proxy_html 2.4.6-97.el7_9.4 Red Hat Enterprise Linux Workstation (v. 7) httpd 2.4.6-97.el7_9.4, mod_ssl 2.4.6-97.el7_9.4, httpd-tools 2.4.6-97.el7_9.4, mod_session 2.4.6-97.el7_9.4, httpd-manual 2.4.6-97.el7_9.4 Red Hat Enterprise Linux Workstation Optional (v. 7) mod_ldap 2.4.6-97.el7_9.4, mod_proxy_html 2.4.6-97.el7_9.4
    fixed: vendor fix RHSA-2022:0143
  • Red Hat JBoss Core Services
    fixed: vendor fix RHSA-2022:7144
  • Red Hat JBoss Core Services on RHEL 7 Server jbcs-httpd24-httpd 2.4.51-28.el7jbcs, jbcs-httpd24-mod_ssl 2.4.51-28.el7jbcs, jbcs-httpd24-mod_ldap 2.4.51-28.el7jbcs, jbcs-httpd24-httpd-tools 2.4.51-28.el7jbcs, jbcs-httpd24-mod_session 2.4.51-28.el7jbcs, jbcs-httpd24-httpd-manual 2.4.51-28.el7jbcs, +2 more Red Hat JBoss Core Services on RHEL 8 jbcs-httpd24-httpd 2.4.51-28.el8jbcs, jbcs-httpd24-mod_ssl 2.4.51-28.el8jbcs, jbcs-httpd24-mod_ldap 2.4.51-28.el8jbcs, jbcs-httpd24-httpd-tools 2.4.51-28.el8jbcs, jbcs-httpd24-mod_session 2.4.51-28.el8jbcs, jbcs-httpd24-httpd-manual 2.4.51-28.el8jbcs, +2 more
    fixed: vendor fix RHSA-2022:7143
  • Red Hat Software Collections for RHEL Workstation(v. 7) httpd24-httpd 2.4.34-23.el7.5, httpd24-mod_ssl 2.4.34-23.el7.5, httpd24-mod_ldap 2.4.34-23.el7.5, httpd24-httpd-tools 2.4.34-23.el7.5, httpd24-mod_session 2.4.34-23.el7.5, httpd24-httpd-manual 2.4.34-23.el7.5, +1 more Red Hat Software Collections for RHEL(v. 7) httpd24-httpd 2.4.34-23.el7.5, httpd24-mod_ssl 2.4.34-23.el7.5, httpd24-mod_ldap 2.4.34-23.el7.5, httpd24-httpd-tools 2.4.34-23.el7.5, httpd24-mod_session 2.4.34-23.el7.5, httpd24-httpd-manual 2.4.34-23.el7.5, +1 more
    fixed: vendor fix RHSA-2022:6753
  • Red Hat Enterprise Linux 9 httpd, mod_lua, mod_ssl, mod_ldap, httpd-core, httpd-tools, +4 more Red Hat JBoss Core Services on RHEL 7 Server jbcs-httpd24-apr 1.7.0-6.el7jbcs, jbcs-httpd24-curl 7.83.1-6.el7jbcs, jbcs-httpd24-brotli 1.0.9-2.el7jbcs, jbcs-httpd24-jansson 2.14-1.el7jbcs, jbcs-httpd24-mod_md 2.4.0-15.el7jbcs, jbcs-httpd24-libcurl 7.83.1-6.el7jbcs, +19 more Red Hat JBoss Core Services on RHEL 8 jbcs-httpd24-apr 1.7.0-6.el8jbcs, jbcs-httpd24-curl 7.83.1-6.el8jbcs, jbcs-httpd24-brotli 1.0.9-2.el8jbcs, jbcs-httpd24-jansson 2.14-1.el8jbcs, jbcs-httpd24-mod_md 2.4.0-15.el8jbcs, jbcs-httpd24-libcurl 7.83.1-6.el8jbcs, +19 more
    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

cisa ICSA-22-167-06 updated cvss 9.8

Siemens Apache HTTP Server

  • Siemens SINEC NMS <V1.0.3
    affected: fixed in V1.0.3, mitigation support.industry.siemens.com
  • Siemens SINEMA Server V14
    affected: mitigation, no fix planned

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

Exploit prediction

39.40% chance of exploitation in the next 30 days, higher than 98% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P
OSV 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
bitnami apache
<2.4.49
2.4.49

Affected products

  • Apache Software Foundation Apache HTTP Server

Classification

Weakness
Technology feeds

References

Sources

Fencer Intel 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.