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 2.13% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2023
CVE-2023-27522High confidence
Apache HTTP Server: mod_proxy_uwsgi HTTP response splitting
Apache Software Foundation · Apache HTTP Server
Official source article: Siemens SSA-943925 ↗. Check the applicable product and release in the original source.
7.5HighCVSS 3.1
Patch only the product branches with a verified fix
Fix availability varies by productHigh technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 12 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityHigh→Operational priority:High, unchanged from published severity.unchanged
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 Apache Software Foundation Apache HTTP Server 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.
Remediation availability differs by product scope
Verified remediation exists for at least one product or source, but 12 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
- Siemens ProductCERT: 1 affected or under-investigation product state without a fixed product state in the same current advisory
- Siemens ProductCERT: 11 affected or under-investigation product states without a fixed product state in the same current advisory
Distribution package intelligence
7 package statesRelease-specific package status
Alpine, 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 |
|---|---|---|---|---|
| Alpine v3.23v3.23 · main | apache2 | Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected. | 2.4.56-r0 | Alpine Security Database ↗Source updated 3 Oct 2026 |
| Alpine v3.22v3.22 · main | apache2 | Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected. | 2.4.56-r0 | Alpine Security Database ↗Source updated 3 Oct 2026 |
| Alpine v3.21v3.21 · main | apache2 | Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected. | 2.4.56-r0 | Alpine Security Database ↗Source updated 3 Oct 2026 |
| Debian trixietrixie · source | apache2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 2.4.56-1 | Debian Security Tracker ↗Source updated 6 Oct 2026 |
| Debian bookwormbookworm · source | apache2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 2.4.56-1 | Debian Security Tracker ↗Source updated 6 Oct 2026 |
| Debian forkyforky · source | apache2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 2.4.56-1 | Debian Security Tracker ↗Source updated 6 Oct 2026 |
| Debian sidsid · source | apache2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 2.4.56-1 | Debian Security Tracker ↗Source updated 6 Oct 2026 |
Direct vendor intelligence
3 currentAuthoritative 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-2023-27522 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityhttpd: mod_proxy_uwsgi HTTP response splitting
The vendor explicitly identifies these products as affected by this CVE.
- httpd as a component of Red Hat Enterprise Linux 6
- httpd-devel as a component of Red Hat Enterprise Linux 6
- httpd-manual as a component of Red Hat Enterprise Linux 6
- httpd-tools as a component of Red Hat Enterprise Linux 6
- httpd.src as a component of Red Hat Enterprise Linux 6
- mod_ssl as a component of Red Hat Enterprise Linux 6
- httpd as a component of Red Hat Enterprise Linux 7
- httpd-devel as a component of Red Hat Enterprise Linux 7
- httpd-manual as a component of Red Hat Enterprise Linux 7
- httpd-tools as a component of Red Hat Enterprise Linux 7
- httpd.src as a component of Red Hat Enterprise Linux 7
- mod_ldap as a component of Red Hat Enterprise Linux 7
- Summary
- An HTTP Response Smuggling vulnerability was found in the Apache HTTP Server via mod_proxy_uwsgi. This security issue occurs when special characters in the origin response header can truncate or split the response forwarded to the client.
- Remediation
- Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
SSA-943925 · CSAF 2.0 · revision 2 · interimSiemens ProductCERTSSA-943925: Multiple Vulnerabilities in SINEC NMS before V2.0 SP1
The vendor explicitly identifies these products as affected by this CVE.
- SINEC NMS
- Summary
- HTTP Response Smuggling vulnerability in Apache HTTP Server via mod_proxy_uwsgi. This issue affects Apache HTTP Server: from 2.4.30 through 2.4.55. Special characters in the origin response header can truncate/split the response forwarded to the client.
- Remediation
- Update to V2.0 SP1 or later version
SSA-806742 · CSAF 2.0 · revision 1 · interimSiemens ProductCERTSSA-806742: Multiple Vulnerabilities in SCALANCE XCM-/XRM-300 before V2.4
The vendor explicitly identifies these products as affected by this CVE.
- SCALANCE XCH328 (6GK5328-4TS01-2EC2)
- SCALANCE XCM324 (6GK5324-8TS01-2AC2)
- SCALANCE XCM328 (6GK5328-4TS01-2AC2)
- SCALANCE XCM332 (6GK5332-0GA01-2AC2)
- SCALANCE XRH334 (24 V DC, 8xFO, CC) (6GK5334-2TS01-2ER3)
- SCALANCE XRM334 (230 V AC, 12xFO) (6GK5334-3TS01-3AR3)
- SCALANCE XRM334 (230 V AC, 8xFO) (6GK5334-2TS01-3AR3)
- SCALANCE XRM334 (24 V DC, 12xFO) (6GK5334-3TS01-2AR3)
- SCALANCE XRM334 (24 V DC, 8xFO) (6GK5334-2TS01-2AR3)
- SCALANCE XRM334 (2x230 V AC, 12xFO) (6GK5334-3TS01-4AR3)
- SCALANCE XRM334 (2x230 V AC, 8xFO) (6GK5334-2TS01-4AR3)
- Summary
- HTTP Response Smuggling vulnerability in Apache HTTP Server via mod_proxy_uwsgi. This issue affects Apache HTTP Server: from 2.4.30 through 2.4.55. Special characters in the origin response header can truncate/split the response forwarded to the client.
- Remediation
- Update to V2.4 or later version
High technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 12 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
Fix availability varies by product01
What, why and how
HTTP Response Smuggling vulnerability in Apache HTTP Server via mod_proxy_uwsgi. This issue affects Apache HTTP Server: from 2.4.30 through 2.4.55. Special characters in the origin response header can truncate/split the response forwarded to the client.
What
HTTP Response Smuggling vulnerability in Apache HTTP Server via mod_proxy_uwsgi. This issue affects Apache HTTP Server: from 2.4.30 through 2.4.55. Special characters in the origin response header can truncate/split the response forwarded to the client.
Why
The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.
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
HTTP Response Smuggling vulnerability in Apache HTTP Server via mod_proxy_uwsgi. This issue affects Apache HTTP Server: from 2.4.30 through 2.4.55. Special characters in the origin response header can truncate/split the response forwarded to the client.
Why
The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.
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 → Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') → 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
- Low: no specialised conditions are recorded
- Security boundary
- Unchanged: impact remains within the vulnerable component's security authority
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-444 ↗
CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling'). The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.
- 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:L/PR:N/UI:N/S:U/C:N/I:H/A:NCommon 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.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.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.CNoneConfidentiality impact: No direct loss is represented by this metric.IHighIntegrity impact: A successful attack can cause a major loss.ANoneAvailability impact: No direct loss is represented by this metric.- 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. - Fix availability varies by product
- Affected
- httpd as a component of Red Hat Enterprise Linux 6
- httpd-devel as a component of Red Hat Enterprise Linux 6
- httpd-manual as a component of Red Hat Enterprise Linux 6
- httpd-tools as a component of Red Hat Enterprise Linux 6
- httpd.src as a component of Red Hat Enterprise Linux 6
- mod_ssl as a component of Red Hat Enterprise Linux 6
- httpd as a component of Red Hat Enterprise Linux 7
- httpd-devel as a component of Red Hat Enterprise Linux 7
- httpd-manual as a component of Red Hat Enterprise Linux 7
- httpd-tools as a component of Red Hat Enterprise Linux 7
- httpd.src as a component of Red Hat Enterprise Linux 7
- mod_ldap as a component of Red Hat Enterprise Linux 7
- mod_proxy_html as a component of Red Hat Enterprise Linux 7
- mod_session as a component of Red Hat Enterprise Linux 7
- mod_ssl as a component of Red Hat Enterprise Linux 7
- httpd22 as a component of Red Hat JBoss Enterprise Application Platform 6
- Fixed
- jbcs-httpd24-httpd-0:2.4.57-5.el7jbcs.src as a component of Red Hat JBoss Core Services on RHEL 7 Server
- jbcs-httpd24-httpd-0:2.4.57-5.el7jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 7 Server
- jbcs-httpd24-httpd-debuginfo-0:2.4.57-5.el7jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 7 Server
- jbcs-httpd24-httpd-devel-0:2.4.57-5.el7jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 7 Server
- jbcs-httpd24-httpd-manual-0:2.4.57-5.el7jbcs.noarch as a component of Red Hat JBoss Core Services on RHEL 7 Server
- jbcs-httpd24-httpd-selinux-0:2.4.57-5.el7jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 7 Server
- jbcs-httpd24-httpd-tools-0:2.4.57-5.el7jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 7 Server
- jbcs-httpd24-mod_ldap-0:2.4.57-5.el7jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 7 Server
- jbcs-httpd24-mod_proxy_html-1:2.4.57-5.el7jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 7 Server
- jbcs-httpd24-mod_session-0:2.4.57-5.el7jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 7 Server
- jbcs-httpd24-mod_ssl-1:2.4.57-5.el7jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 7 Server
- jbcs-httpd24-httpd-0:2.4.57-5.el8jbcs.src as a component of Red Hat JBoss Core Services on RHEL 8
- jbcs-httpd24-httpd-0:2.4.57-5.el8jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 8
- jbcs-httpd24-httpd-debuginfo-0:2.4.57-5.el8jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 8
- jbcs-httpd24-httpd-devel-0:2.4.57-5.el8jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 8
- jbcs-httpd24-httpd-manual-0:2.4.57-5.el8jbcs.noarch as a component of Red Hat JBoss Core Services on RHEL 8
- jbcs-httpd24-httpd-selinux-0:2.4.57-5.el8jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 8
- jbcs-httpd24-httpd-tools-0:2.4.57-5.el8jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 8
- jbcs-httpd24-httpd-tools-debuginfo-0:2.4.57-5.el8jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 8
- jbcs-httpd24-mod_ldap-0:2.4.57-5.el8jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 8
- jbcs-httpd24-mod_ldap-debuginfo-0:2.4.57-5.el8jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 8
- jbcs-httpd24-mod_proxy_html-1:2.4.57-5.el8jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 8
- jbcs-httpd24-mod_proxy_html-debuginfo-1:2.4.57-5.el8jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 8
- jbcs-httpd24-mod_session-0:2.4.57-5.el8jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 8
- jbcs-httpd24-mod_session-debuginfo-0:2.4.57-5.el8jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 8
- jbcs-httpd24-mod_ssl-1:2.4.57-5.el8jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 8
- jbcs-httpd24-mod_ssl-debuginfo-1:2.4.57-5.el8jbcs.x86_64 as a component of Red Hat JBoss Core Services on RHEL 8
- httpd-0:2.4.37-47.module+el8.6.0+19809+6e655c60.7.aarch64 (httpd:2.4) as a component of Red Hat Enterprise Linux AppStream EUS (v.8.6)
- httpd-0:2.4.37-47.module+el8.6.0+19809+6e655c60.7.ppc64le (httpd:2.4) as a component of Red Hat Enterprise Linux AppStream EUS (v.8.6)
- httpd-0:2.4.37-47.module+el8.6.0+19809+6e655c60.7.s390x (httpd:2.4) as a component of Red Hat Enterprise Linux AppStream EUS (v.8.6)
- and 317 more
- Action
- Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
- 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.
04
Evidence and provenance
Published 7 Mar 2023 · Last source change 13 Feb 2025, 16:45 UTC · CWE-444 · Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
CVE recordCVE.org · 5.1
CVSS sourceNIST NVD
EPSS source FIRST · tracked since 2026-08-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2023-1108
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD enriched
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- 2.4.30 ≤ 2.4.55 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
- After
- 2.4.30 ≤ 2.4.55 · Fixed: Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
- Remediation statusRemediation status changed from Mitigation available to Patch available.Red Hat Product Security ↗
- Before
- Mitigation available
- After
- Patch available
- Remediation statusRemediation status changed from Awaiting fix to Mitigation available.Siemens ProductCERT ↗
- Before
- Awaiting fix
- After
- Mitigation available
CVE published
Remediation guidance 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.