CVE-2021-20325Network attack vector

SSRF and heap overflow via missing backports

Published Feb 18, 2022 · Updated Aug 3, 2024

Security regression in RHEL 8.5.0 httpd allows remote attackers to induce SSRF or memory corruption through crafted HTTP traffic. Missing backports let mod_proxy forward an attacker-chosen request URI to an origin server and let mod_session copy a crafted SessionHeader beyond a heap buffer. The SSRF path requires mod_proxy, while the heap overflow requires nondefault SessionEnv plus control of an origin response and can crash an httpd child process.

CVSS severity9.0
Critical
EPSS probability1.59%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Security regression in RHEL 8.5.0 httpd allows remote attackers to induce SSRF or memory corruption through crafted HTTP traffic. Missing backports let mod_proxy forward an attacker-chosen request URI to an origin server and let mod_session copy a crafted SessionHeader beyond a heap buffer. The SSRF path requires mod_proxy, while the heap overflow requires nondefault SessionEnv plus control of an origin response and can crash an httpd child process.

The record

CVE
CVE-2021-20325
Published
Feb 18, 2022
Updated
Aug 3, 2024
Vendor
Red Hat
Product
Red Hat Enterprise Linux
Classifications
CWE-918, CWE-119, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 18, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=httpd 2.4.47, httpd 2.4.49

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Red Hat · Red Hat Enterprise Linuxversion=httpd 2.4.47, httpd 2.4.49

Published CVSS scores

9.0Red HatCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-918Server-Side Request Forgery (SSRF)
CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo