CVE-2021-40438
mod_proxy SSRF
- Published
- Updated
- Reserved
- Assigned by
- apache
Description
A crafted request uri-path can cause mod_proxy to forward the request to an origin server choosen by the remote user. This issue affects Apache HTTP Server 2.4.48 and earlier.
Exploited in the wild
CISA lists this vulnerability in its Known Exploited Vulnerabilities catalog as Apache HTTP Server-Side Request Forgery (SSRF).
- Added
- 1 Dec 2021
- Fix due (US federal)
- 15 Dec 2021
- Used by ransomware
- Known
Apply updates per vendor instructions.
Public exploit
An exploit or proof of concept is public: anyone can try it against an unpatched system. CISA's SSVC rates its exploitation: it is being exploited.
Timeline
ID reserved
By apache
- 14 days later
· 14 days later
Published
- 3 months later
· 3 months later
Added to CISA KEV
Known exploited, also by ransomware
- 5 years later
· 5 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| CISA-ADPADP (enrichment) | 3.1 | Critical9.0 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H |
| NVDNVD · Analyzed | 3.1 | Critical9.0 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 100.0% · top 0.1% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: active · Automatable: yes · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.0.
Weakness
Affected products
Apache Software Foundation · Apache HTTP Server
- affected Apache HTTP Server 2.4 – ≤ 2.4.48
References (20)
- https://httpd.apache.org/security/vulnerabilities_24.html (opens in a new tab)x_refsource_MISCx_transferred
- FEDORA-2021-dce7e7738e (opens in a new tab)vendor-advisoryx_refsource_FEDORAx_transferred
- [httpd-users] 20210923 [users@httpd] 2.4.49 security fixes: more info (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
- [httpd-users] 20210923 Re: [users@httpd] 2.4.49 security fixes: more info (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
- [httpd-users] 20210923 [users@httpd] Re: [External] : [users@httpd] 2.4.49 security fixes: more info (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
- [httpd-users] 20210923 Re: [users@httpd] Re: [External] : [users@httpd] 2.4.49 security fixes: more info (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
- FEDORA-2021-e3f6dd670d (opens in a new tab)vendor-advisoryx_refsource_FEDORAx_transferred
- [debian-lts-announce] 20211002 [SECURITY] [DLA 2776-1] apache2 security update (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
- [httpd-bugs] 20211008 [Bug 65616] CVE-2021-36160 regression (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
- DSA-4982 (opens in a new tab)vendor-advisoryx_refsource_DEBIANx_transferred
- [httpd-users] 20211019 [users@httpd] Regarding CVE-2021-40438 (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
- [httpd-users] 20211019 Re: [users@httpd] Regarding CVE-2021-40438 (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
- 20211124 Multiple Vulnerabilities in Apache HTTP Server Affecting Cisco Products: November 2021 (opens in a new tab)vendor-advisoryx_refsource_CISCOx_transferred
- https://www.oracle.com/security-alerts/cpujan2022.html (opens in a new tab)x_refsource_MISCx_transferred
- https://www.tenable.com/security/tns-2021-17 (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://security.netapp.com/advisory/ntap-20211008-0004/ (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://www.oracle.com/security-alerts/cpuapr2022.html (opens in a new tab)x_refsource_MISCx_transferred
- https://cert-portal.siemens.com/productcert/pdf/ssa-685781.pdf (opens in a new tab)x_refsource_CONFIRMx_transferred
- GLSA-202208-20 (opens in a new tab)vendor-advisoryx_refsource_GENTOOx_transferred
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40438 (opens in a new tab)government-resource
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- CISA KEV catalog (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2021-40438)Record last updated .