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CVE Record

CVE-2026-49975: Apache HTTP Server: mod_http2 denial of service

Memory Allocation with Excessive Size Value vulnerability in Apache HTTP Server's mod_http leads to denial of service via malicious HTTP requests. This issue affects Apache HTTP Server: from 2.4.17 through 2.4.67.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-49975 is a denial-of-service flaw in Apache HTTP Server affecting versions 2.4.17 through 2.4.67. Malicious HTTP requests can trigger excessive memory allocation, potentially taking a web service down. The impact is availability, not data theft or code execution based on the provided sources.

Executive priority

High priority for externally reachable Apache services because exploitation can disrupt customer-facing web availability. There is no evidence in the provided sources of data compromise or confirmed active exploitation, but public exploit reference and network reachability justify timely remediation.

Technical view

The record describes a memory allocation with excessive size value issue in Apache HTTP Server mod_http2, mapped to CWE-409 and CWE-789. It is remotely reachable, unauthenticated, low complexity, and rated CVSS 7.5 because successful exploitation can cause high availability impact.

Likely exposure

Organizations running Apache HTTP Server 2.4.17 through 2.4.67, particularly internet-facing deployments using the affected HTTP/2 module, should assess exposure. Distribution-packaged Apache builds may have separate backport status, so validate against Apache, Debian, and Red Hat guidance.

Exploitation context

The bundle lists a public GitHub exploit reference, but KEV status is false and no cited source here confirms active exploitation in the wild. Treat public exploit availability as a reason to prioritize validation and patch tracking without assuming confirmed attacks.

Researcher notes

Evidence supports remote unauthenticated denial of service via excessive memory allocation. The source bundle does not provide safe reproduction details or exact fixed upstream version text, so validation should focus on version/module exposure and vendor advisory status rather than exploit testing.

Mitigation direction

  • Check Apache HTTP Server advisory for fixed versions or configuration guidance.
  • Apply relevant vendor updates from Apache or your Linux distribution.
  • Review Debian LTS and Red Hat advisories for package-specific remediation status.
  • Prioritize internet-facing Apache servers before internal-only systems.
  • Consider temporary exposure reduction if updates are not immediately available.

Validation and detection

  • Inventory Apache HTTP Server versions across production and edge hosts.
  • Confirm whether deployed versions fall within 2.4.17 through 2.4.67.
  • Check whether the affected HTTP/2 module is enabled.
  • Map installed OS packages to Debian or Red Hat advisory status.
  • Monitor web server availability and memory pressure for abnormal request-driven spikes.
Prepared
Confidence
medium
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-409: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-789: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-49975 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
9Timeline events
3ADP providers
17Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6CISA-ADP
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-49975Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. Source timelineapache

    reported

  2. Source timelineapache

    fixed upstream in mod_h2 https://github.com/icing/mod_h2/commit/35c6e405390ed361189a82acd96675401ea5947c

  3. Source timelineapache

    fixed in 2.4.x by r1934882

  4. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  5. ADP timelineredhat-SADP

    Made public.

  6. ADP timelineredhat-SADP

    Reported to Red Hat.

  7. Source timelineapache

    2.4.68 released

  8. CVE publishedCVE Program

    The CVE record was published.

  9. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
redhat-SADPhttpd: httpd: HTTP/2 Remote Denial of Service via compression bomb and Slowloris-style attack
other:Red Hat severity ratingcvssV3_1
  • 2026-06-05T06:04:44.009Z: Reported to Red Hat.
  • 2026-06-03T00:00:00.000Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Apache Software FoundationApache HTTP Server2.4.17unaffected
Weakness

CWE details

CWE-409CWE-789

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-409 · source CWE mapping

Improper Handling of Highly Compressed Data (Data Amplification)

Improper Handling of Highly Compressed Data (Data Amplification) represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-789 · source CWE mapping

Memory Allocation with Excessive Size Value

Memory Allocation with Excessive Size Value represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs