Evidence used
- No CISA KEV confirmation is currently recorded.
- The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
- EPSS is 55.72% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2016
CVE-2016-5387High confidence
Affected product: security vulnerability
Unknown · Unknown
8.1HighCVSS 3.1
Within 7 days
Patch availableHigh technical severity; prioritise exposed affected systems while verifying vendor guidance.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityHigh→Operational priority:Critical, raised one band.upgradedsince 22 Oct 2026
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict the affected network interface to trusted sources where business-safe.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs Unknown Unknown and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Distribution package intelligence
4 package statesRelease-specific package status
Debian findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.
Repository candidate not checked
A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.
| Distribution release | Source package | Vendor state | Fixed version | Evidence |
|---|---|---|---|---|
| Debian trixietrixie · source | apache2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 2.4.23-2 | Debian Security Tracker ↗Source updated 22 Oct 2026 |
| Debian bookwormbookworm · source | apache2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 2.4.23-2 | Debian Security Tracker ↗Source updated 22 Oct 2026 |
| Debian forkyforky · source | apache2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 2.4.23-2 | Debian Security Tracker ↗Source updated 22 Oct 2026 |
| Debian sidsid · source | apache2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 2.4.23-2 | Debian Security Tracker ↗Source updated 22 Oct 2026 |
Direct vendor intelligence
0 current · 1 archivedAuthoritative vendor CSAF and VEX advisories
Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.
CVE-2016-5387 · CSAF 2.0 · revision 3 · finalRed Hat Product SecurityHTTPD: sets environmental variable based on user supplied Proxy request headerNo longer in the provider’s current catalogue
The vendor explicitly identifies these products as affected by this CVE.
- httpd22 as a component of Red Hat JBoss Enterprise Application Platform 6
- httpd.src as a component of Red Hat JBoss Enterprise Web Server 1
- Summary
- It was discovered that httpd used the value of the Proxy header from HTTP requests to initialize the HTTP_PROXY environment variable for CGI scripts, which in turn was incorrectly used by certain HTTP client implementations to configure the proxy for outgoing HTTP requests. A remote attacker could possibly use this flaw to redirect HTTP requests performed by a CGI script to an attacker-controlled proxy via a malicious HTTP request.
- Remediation
- For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 After installing the updated packages, the httpd daemon will be restarted automatically.
High technical severity; prioritise exposed affected systems while verifying vendor guidance.
Patch available01
What, why and how
The Apache HTTP Server through 2.4.23 follows RFC 3875 section 4.1.18 and therefore does not protect applications from the presence of untrusted client data in the HTTP_PROXY environment variable, which might allow remote attackers to redirect an application's outbound HTTP traffic to an arbitrary proxy server via a crafted Proxy header in an HTTP request, aka an "httpoxy" issue. NOTE: the vendor states "This mitigation has been assigned the identifier CVE-2016-5387"; in other words, this is not a CVE ID for a vulnerability.
What
The Apache HTTP Server through 2.4.23 follows RFC 3875 section 4.1.18 and therefore does not protect applications from the presence of untrusted client data in the HTTP_PROXY environment variable, which might allow remote attackers to redirect an application's outbound HTTP traffic to an arbitrary proxy server via a crafted Proxy header in an HTTP request, aka an "httpoxy" issue. NOTE: the vendor states "This mitigation has been assigned the identifier CVE-2016-5387"; in other words, this is not a CVE ID for a vulnerability.
Why
The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
The Apache HTTP Server through 2.4.23 follows RFC 3875 section 4.1.18 and therefore does not protect applications from the presence of untrusted client data in the HTTP_PROXY environment variable, which might allow remote attackers to redirect an application's outbound HTTP traffic to an arbitrary proxy server via a crafted Proxy header in an HTTP request, aka an "httpoxy" issue. NOTE: the vendor states "This mitigation has been assigned the identifier CVE-2016-5387"; in other words, this is not a CVE ID for a vulnerability.
Why
The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- a network path → vulnerable operation → cause the confidentiality, integrity or availability impact described by the vendor
- Attack surface
- Network
- Privileges required
- None: unauthenticated exploitation is possible
- User interaction
- None
- Attack complexity
- High: exploitation depends on specific conditions
- Security boundary
- Unchanged: impact remains within the vulnerable component's security authority
- Weakness
?
CWE means Common Weakness Enumeration. - CWE not yet assigned
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:HCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.- Post-exploitation / living off the land
- No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Patch available
- Affected
- n/a
- Action
- Apply the fixed release for the affected product branch as recorded by Red Hat Product Security. Validate the exact product and build in the linked advisory before deployment.
- Workaround
- No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
Official vendor articles4 stored documents
Linked articles are downloaded and versioned as source evidence. A CVE mention or approved update relationship does not, by itself, verify a fix for every product branch.
- About the security content of macOS Sierra 10.12.4, Security Update 2017-001 El Capitan, and Security Update 2017-001 Yosemite - Apple Support →Original publisher ↗Searchable text snapshot · Captured 17 Oct 2026Apple Store Mac iPad iPhone Watch Vision AirPods Home Entertainment Accessories Support 0 + "},{"name":"compact","assetInline":" "}],"analyticsAttributes":[{"name":"data-analytics-title","value":"apple home"}]},{"id":"ad4a2a26eb4836393385e9f6c61b526b4a3cb31409c5ed8730ce7a704dd7132f","name":"store","text":"
- About the security content of macOS High Sierra 10.13 - Apple Support →Original publisher ↗Searchable text snapshot · Captured 17 Oct 2026Apple Store Mac iPad iPhone Watch Vision AirPods Home Entertainment Accessories Support 0 + "},{"name":"compact","assetInline":" "}],"analyticsAttributes":[{"name":"data-analytics-title","value":"apple home"}]},{"id":"ad4a2a26eb4836393385e9f6c61b526b4a3cb31409c5ed8730ce7a704dd7132f","name":"store","text":"
- About the security content of macOS High Sierra 10.13.1, Security Update 2017-001 Sierra, and Security Update 2017-004 El Capitan - Apple Support →Original publisher ↗Searchable text snapshot · Captured 17 Oct 2026Apple Store Mac iPad iPhone Watch Vision AirPods Home Entertainment Accessories Support 0 + "},{"name":"compact","assetInline":" "}],"analyticsAttributes":[{"name":"data-analytics-title","value":"apple home"}]},{"id":"ad4a2a26eb4836393385e9f6c61b526b4a3cb31409c5ed8730ce7a704dd7132f","name":"store","text":"
- asf-httpoxy-response.txt →Original publisher ↗Searchable text snapshot · Captured 27 Sep 2026Advisory: Apache Software Foundation Projects and "httpoxy" CERT VU#797896 Canonical URL: https://www.apache.org/security/asf-httpoxy-response.txt Publication: v1.0 18 July 2016 Audience -------- This Advisory is directed to HTTP web server administrators and users of the software indicated below, including CGI d
04
Evidence and provenance
Published 19 Jul 2016 · Last source change 6 Aug 2024, 01:00 UTC · CWE not yet assigned
CVE recordCVE.org · 5.1
CVSS sourceNIST NVD
EPSS source FIRST · tracked since 2026-09-01
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2016-6337
Product sourceUnavailable
Remediation sourceCVE/CNA references
CWE sourceUnavailable
NVD statusNVD modified after enrichment
Missing structured fields: CWE classification, affected product. Missing data is not evidence of low risk; review the primary advisory.
Material change intelligence
View recent updates ↗What changed after publication
- Vendor guidanceAuthoritative vendor guidance changed from remediation: access.redhat.com/CVE-2016-5387 to advisory no longer present in the provider's current catalogue.Red Hat Product Security ↗
- Before
- remediation: access.redhat.com/CVE-2016-5387
- After
- advisory no longer present in the provider's current catalogue
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- n/a · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
- After
- n/a · Fixed: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 After installing the updated packages, the httpd daemon will be restarted automatically.
- ENISA EUVD mappingEUVD-2016-6337 was added to the official ENISA EUVD mapping for this CVE.ENISA EUVD ↗
- Before
- not recorded
- After
- {"euvdId":"EUVD-2016-6337"}
- Vendor guidanceAuthoritative vendor guidance changed: added patch: oracle.com/cpujan2018-3236628.html; added patch: oracle.com/cpujul2017-3236622.html; removed vendor advisory: access.redhat.com/RHSA-2016:1420; removed vendor advisory: access.redhat.com/RHSA-2016:1421; 2 further additions; 17 further removals.oracle.com ↗
- Before
- vendor advisory: access.redhat.com/RHSA-2016:1420 · vendor advisory: access.redhat.com/RHSA-2016:1421 · vendor advisory: access.redhat.com/RHSA-2016:1422 · 16 more references
- After
- patch: oracle.com/cpujan2018-3236628.html · patch: oracle.com/cpujul2017-3236622.html · remediation: oracle.com/cpujan2018-3236628.html · 1 more references
- Affected versionsThe structured affected or fixed version information changed.CNA ↗
- Before
- n/a · Fixed: No fixed version is explicitly recorded in the structured CVE data.
- After
- n/a · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
- Remediation statusRemediation status changed from Awaiting fix to Patch available.oracle.com ↗
- Before
- Awaiting fix
- After
- Patch available
- SeveritySeverity changed from Unknown to High.NIST NVD ↗
- Before
- Unknown
- After
- High
- CVSS scoreCVSS score changed from not recorded to 8.1 (CVSS 3.1 · NIST NVD · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H).NIST NVD ↗
- Before
- not recorded
- After
- 8.1 (CVSS 3.1 · NIST NVD · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H)
- Catalogue recordCVE added to the BlackTree catalogue.CNA ↗
CVE published
Fixed release or patch reference recorded
Fixed release recorded from official guidance
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.