LiveActive security incident?Get immediate response
CVE Record

CVE-2021-39275: ap_escape_quotes buffer overflow

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.

UnknownCVSS not scoredNot KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

Apache HTTP Server 2.4.48 and earlier contained a buffer overflow in a quote-escaping helper. Apache says bundled modules do not pass untrusted data into this function, so typical exposure depends on third-party or external modules. Treat it as important maintenance risk, not confirmed internet-wide exploitation.

Executive priority

Handle through normal vulnerability remediation unless a business-critical system runs old Apache with custom or third-party modules. No active exploitation is evidenced in the bundle, but the memory-corruption class and Apache's wide deployment justify timely patching.

Technical view

CVE-2021-39275 is an out-of-bounds write in ap_escape_quotes(). Malicious input could trigger memory corruption if a module passes attacker-controlled data to the helper. The public description limits likely reach: no included Apache modules are identified as doing that, but third-party or external modules may.

Likely exposure

Internet-facing Apache HTTP Server 2.4.48 or earlier is relevant, especially where custom, third-party, or vendor-embedded modules are installed. Standard bundled-module deployments appear lower risk based on Apache's statement, but embedded products from vendors may still need their own advisories checked.

Exploitation context

The source bundle does not show CISA KEV listing, public exploitation confirmation, exploit code, or a proven bundled-module attack path. Risk depends on whether external module code feeds untrusted input to ap_escape_quotes().

Researcher notes

The key technical question is reachability, not just version. The affected function exists in Apache httpd, but the CVE text says bundled modules do not pass untrusted data to it. Validate external module call paths and vendor-embedded Apache packages.

Mitigation direction

  • Upgrade Apache HTTP Server using Apache or OS vendor security guidance.
  • Do not remain on Apache HTTP Server 2.4.48 or earlier.
  • Inventory third-party and custom Apache modules for affected helper usage.
  • Check embedded appliance advisories from Cisco, NetApp, Oracle, Siemens, and other vendors.
  • Prioritize externally exposed servers before internal-only instances.

Validation and detection

  • Confirm Apache HTTP Server version on all managed hosts and images.
  • List enabled third-party, custom, and vendor-supplied Apache modules.
  • Review module code or vendor notes for ap_escape_quotes() exposure to untrusted input.
  • Verify OS package advisories have been applied for apache2/httpd packages.
  • Check internet-facing asset inventory for Apache 2.4.48 or earlier.
Prepared
Confidence
medium
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cve · low confidence lookup

CVE-2021-39275 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
16Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Apache Software FoundationApache HTTP ServerApache HTTP Server 2.4Listed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.