cbcvebase.
CVE-2021-39275
published 2021-09-16

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…

PriorityP268critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
39.40%
98.5th percentile
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.

Affected

18 ranges
VendorProductVersion rangeFixed in
apachehttp_server< 2.4.492.4.49
apache_software_foundationapache_http_serverApache HTTP Server 2.4 – 2.4.48
debianapache2< apache2 2.4.49-1 (bookworm)apache2 2.4.49-1 (bookworm)
debiandebian_linux
debiandebian_linux
debiandebian_linux
fedoraprojectfedora
fedoraprojectfedora
msrccbl2_httpd_2.4.52-1_on_cbl_mariner_2.0
msrccm1_httpd_2.4.49-1_on_cbl_mariner_1.0
oraclehttp_server
oraclehttp_server
oracleinstantis_enterprisetrack
oracleinstantis_enterprisetrack
oracleinstantis_enterprisetrack
oraclezfs_storage_appliance_kit
paloaltopan-os
siemenssinema_server

Detection & IOCsextracted from sources · hover to see the quote

  • The vulnerable function is ap_escape_quotes() in Apache HTTP Server — monitor for out-of-bounds write conditions triggered by malicious input passed to this function via third-party/external modules.
  • Restrict and monitor access to Port 443/TCP on affected Apache HTTP Server deployments (specifically Siemens RUGGEDCOM NMS, SINEC NMS, SINEMA Remote Connect Server, SINEMA Server v14) as a mitigation indicator.
  • ·No built-in Apache HTTP Server modules pass untrusted data to ap_escape_quotes(); exploitation requires a third-party or external module to be present that does so. Assess deployed third-party modules before prioritizing this CVE.
  • ·Red Hat confirmed no httpd module in RHEL or Red Hat Software Collections passes untrusted data to ap_escape_quotes, reducing practical impact in those environments.
  • ·Affected versions are Apache HTTP Server 2.4.48 and earlier; fixed in 2.4.49. Verify the running httpd version to confirm exposure.
  • ·No known public exploits specifically target this vulnerability as of the CISA advisory publication.

CVSS provenance

nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
nvdv2.07.5HIGHAV:N/AC:L/Au:N/C:P/I:P/A:P
osv9.8CRITICAL
vendor_debian9.8CRITICAL
vendor_msrc9.8CRITICAL
vendor_oracle9.8CRITICAL
vendor_redhat9.8CRITICAL
vendor_cisco9.0CRITICAL
vendor_ubuntu7.5HIGH
Stop checking back — get the weekly exploitation signal.

Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.