CVE-2017-9788: In Apache httpd before 2.2.34 and 2.4.x before 2.4.27, the value placeholder in [Proxy-]Authorization headers of type…

Is it exploited?

Reported, not confirmed by CISA. VulnCheck KEV lists it as exploited in the wild. CISA has not added it to its Known Exploited Vulnerabilities catalog as of 29 Oct 2026.

VulnCheck KEV lists it since 22 Feb 2022. It cites 1 public report, the first from 22 Feb 2022.

• trendmicro.com

How likely is exploitation in the next 30 days?

56.8%

EPSS score, percentile 99.1 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

Not scored

The CVE record carries no CVSS score.

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

Advisories and patches (12)

Which versions are affected?

Affected

• 2.2.0 to 2.2.33
• 2.4.1 to 2.4.26

Versions by product

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; VulnCheck KEV, as of 30 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 30 Oct 2026. About the data.

Description

In Apache httpd before 2.2.34 and 2.4.x before 2.4.27, the value placeholder in [Proxy-]Authorization headers of type 'Digest' was not initialized or reset before or between successive key=value assignments by mod_auth_digest. Providing an initial key with no '=' assignment could reflect the stale value of uninitialized pool memory used by the prior request, leading to leakage of potentially confidential information, and a segfault in other cases resulting in denial of service.

Source: CVE List, as of 30 Oct 2026. About the data.

What to do

Advisories and patches

• RHSA-2017:3113 (Vendor advisory)
• RHSA-2017:2479 (Vendor advisory)
• RHSA-2017:2483 (Vendor advisory)
• RHSA-2017:3240 (Vendor advisory)
• RHSA-2017:2709 (Vendor advisory)
• RHSA-2017:3195 (Vendor advisory)
• RHSA-2017:3239 (Vendor advisory)
• RHSA-2017:3114 (Vendor advisory)
• RHSA-2017:3194 (Vendor advisory)
• RHSA-2017:3193 (Vendor advisory)
• RHSA-2017:2710 (Vendor advisory)
• DSA-3913 (Vendor advisory)

This summary is based on the CVE record as of 30 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

Source: CVE List, as of 30 Oct 2026. About the data.

Timeline

Known exploited Apache vulnerabilities

• CVE-2016-3081: Apache Struts Command Injection Vulnerability (added 8 Oct 2026)
• CVE-2026-34486: Apache Tomcat Missing Encryption of Sensitive Data Vulnerability (added 4 Aug 2026)
• CVE-2026-34197: Apache ActiveMQ Improper Input Validation Vulnerability (added 16 Apr 2026)
• CVE-2024-38475: Apache HTTP Server Improper Escaping of Output Vulnerability (added 1 May 2025)
• CVE-2025-24813: Apache Tomcat Path Equivalence Vulnerability (added 1 Apr 2025)