CVE-2016-0736HTTP Server Authentication Bypass
In Apache HTTP Server versions 2.4.0 to 2.4.23, mod_session_crypto was encrypting its data/cookie using the configured ciphers with possibly either CBC or ECB modes of operation (AES256-CBC by default), hence no selectable or builtin authenticated encryption.
Published Jul 27, 2017 · Updated Sep 23, 2026 · Also known as DEBIAN-CVE-2016-0736, DSA-3796-1, SUSE-SU-2017:0797-1, SUSE-SU-2017:0801-1, UBUNTU-CVE-2016-0736, USN-3279-1
Key Facts
Patch immediately- CVE-2016-0736 is a high-severity vulnerability (CVSS 7.5 v3.1) affecting HTTP Server (Apache), apache2 (debian), rootio-apache2 and 22 more products.
- It is exploited in the wild, listed in Industry KEV feed since Feb 14, 2023. A public exploit is reported by tracking sources, but no code link is listed yet.
- EPSS estimates a 49% probability of exploitation in the next 30 days.
- Fixed versions are available, including apache2 2.4.10-10+deb8u8, apache2 2.4.16-18.1, apache2 2.4.16-19.1.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
Scores
CVSS v3.1
7.5
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS (30-day exploit likelihood)
49%
Higher than 98.8% of all scored CVEs
Exploit maturity
Proof of concept
ATLAS score
46/100
Publication score, see How it works
Exploitation Verdict
KEV listed
Feb 14, 2023
Federal due date
None
No federal due date
Ransomware use
Not reported
Attributed actors
None named
Exploit & Defence Guidance
Exploit maturity
Proof of concept
Public exploit code
1
Proof-of-concept links
In-the-wild evidence
1
Reports of active use
Advisories And Exploit References
Description
In Apache HTTP Server versions 2.4.0 to 2.4.23, mod_session_crypto was encrypting its data/cookie using the configured ciphers with possibly either CBC or ECB modes of operation (AES256-CBC by default), hence no selectable or builtin authenticated encryption. This made it vulnerable to padding oracle attacks, particularly with CBC.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| Industry KEV feed | Feb 14, 2023 | n/a | Not reported |
Affected Products
113 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| HTTP ServerApache | 2.4.0, 2.4.1, 2.4.10, 2.4.12, 2.4.14, 2.4.16, 2.4.19, 2.4.2 | n/a |
| apache2debian | See advisory | 2.4.25-1 |
| rootio-apache2rootio | See advisory | 2.4.25-1 |
| httpd24-develamazon | See advisory | 2.4.25-1.68.amzn1 |
| httpd24amazon | See advisory | 2.4.25-1.68.amzn1 |
Patched Releases
apache2
2.4.10-10+deb8u8, 2.4.16-18.1, 2.4.16-19.1, 2.4.18-2ubuntu3.2, 2.4.23-21.1, 2.4.23-8.3.1, 2.4.25-1, 2.4.7-1ubuntu4.15
apache2-devel
2.4.16-18.1, 2.4.16-19.1, 2.4.23-21.1, 2.4.23-8.3.1
apache2-doc
2.4.16-18.1, 2.4.16-19.1, 2.4.23-21.1, 2.4.23-8.3.1
apache2-event
2.4.16-18.1, 2.4.23-8.3.1
apache2-example-pages
2.4.16-18.1, 2.4.16-19.1, 2.4.23-21.1, 2.4.23-8.3.1
apache2-prefork
2.4.16-18.1, 2.4.16-19.1, 2.4.23-21.1, 2.4.23-8.3.1
apache2-utils
2.4.16-18.1, 2.4.16-19.1, 2.4.23-21.1, 2.4.23-8.3.1
apache2-worker
2.4.16-18.1, 2.4.16-19.1, 2.4.23-21.1, 2.4.23-8.3.1
httpd
0:2.4.6-45.el7_3.4, 2.4.6-45.0.1.el7_3.4
httpd-devel
2.4.6-45.0.1.el7_3.4
httpd-manual
2.4.6-45.0.1.el7_3.4
httpd-tools
2.4.6-45.0.1.el7_3.4
httpd24
2.4.25-1.68.amzn1
httpd24-devel
2.4.25-1.68.amzn1
httpd24-httpd
0:2.4.25-9.el6, 0:2.4.25-9.el7
httpd24-manual
2.4.25-1.68.amzn1
httpd24-tools
2.4.25-1.68.amzn1
jbcs-httpd24-httpd
0:2.4.23-120.jbcs.el6, 0:2.4.23-120.jbcs.el7
jbcs-httpd24-mod_security
0:2.9.1-19.GA.jbcs.el6, 0:2.9.1-19.GA.jbcs.el7
jbcs-httpd24-openssl
1:1.0.2h-13.jbcs.el6, 1:1.0.2h-13.jbcs.el7
mod_ldap
2.4.6-45.0.1.el7_3.4
mod_proxy_html
1:2.4.6-45.0.1.el7_3.4
mod_session
2.4.6-45.0.1.el7_3.4
mod_ssl
1:2.4.6-45.0.1.el7_3.4
mod24_ldap
2.4.25-1.68.amzn1
Timeline
Publicly disclosed
Jul 27, 2017
Added to Industry KEV feed
Feb 14, 2023
Last updated
Sep 23, 2026
Weakness Type
- CWE-287 Improper Authentication
- CWE-310
References
- advisoryhttpd.apache.org · vulnerabilities_24.html
- advisorysecurity-tracker.debian.org · CVE-2016-0736
- advisoryubuntu.com · CVE-2016-0736
- advisorycve.org · CVERecord
- advisoryRHSA-2017:0906
FAQ
Common Questions.
In Apache HTTP Server versions 2.4.0 to 2.4.23, mod_session_crypto was encrypting its data/cookie using the configured ciphers with possibly either CBC or ECB modes of operation (AES256-CBC by default), hence no selectable or builtin authenticated encryption.
Affected: HTTP Server (Apache) versions 2.4.0, 2.4.1, 2.4.10, 2.4.12, 2.4.14, 2.4.16, 2.4.19, 2.4.2; apache2 (debian); rootio-apache2, among others. The full list is in the CVE brief.
It is exploited in the wild, listed in Industry KEV feed since Feb 14, 2023.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
A public exploit is reported by tracking sources, but no code link is listed yet.
Fixed versions are available, including apache2 2.4.10-10+deb8u8, apache2 2.4.16-18.1, apache2 2.4.16-19.1.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
Is CVE-2016-0736 On Your Attack Surface?
Brandefense matches it against the products discovered on your perimeter and opens a finding the day a CVE like this is listed.
Request A Demo