Apache HTTP Server: Memory Allocation with Excessive Size Value
CVE-2026-49975 is a high-severity memory allocation with excessive size value vulnerability in Apache HTTP Server from Apache, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Apache HTTP Server versions: 2.4.17 through 2.4.67. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 33% chance of exploitation within 30 days, which is in the top 1.62% of all scored CVEs.
EPSS places it among the vulnerabilities most likely to be exploited soon.
What to do
- Update HTTP Server to 2.4.68 or a later version.
- Read the advisory on httpd.apache.org for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.5 | High | CISA (ADP) |
| CVSS 3.1 | 7.5 | High | CNA |
Official description
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Memory Allocation with Excessive Size Value
The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.
How developers prevent this class of flaw
- Perform adequate input validation against any value that influences the amount of memory that is allocated. Define an appropriate strategy for handling requests that exceed the limit, and consider supporting a configuration option so that the administrator can extend the amount of memory to be used if necessary.
- Run your program using system-provided resource limits for memory. This might still cause the program to crash or exit, but the impact to the rest of the system will be minimized.
More Memory Allocation with Excessive Size Value vulnerabilities (CWE-789)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- openwall.com/lists/oss-security/2026/06/03/3Mailing List, Third Party Advisory
- openwall.com/lists/oss-security/2026/06/08/16Mailing List, Third Party Advisory
- lists.debian.org/debian-lts-announce/2026/06/msg00009.htmlMailing List, Third Party Advisory
Technical write-ups (may include proof of concept)
- github.com/EQSTLab/CVE-2026-49975Exploit, Third Party Advisory
Other references
- access.redhat.com/errata/RHSA-2026:25042
- access.redhat.com/errata/RHSA-2026:25057
- access.redhat.com/errata/RHSA-2026:25090
- access.redhat.com/errata/RHSA-2026:25225
- access.redhat.com/errata/RHSA-2026:27114
- access.redhat.com/errata/RHSA-2026:27200
- access.redhat.com/errata/RHSA-2026:27201
- access.redhat.com/errata/RHSA-2026:36373
- access.redhat.com/errata/RHSA-2026:36831
- access.redhat.com/errata/RHSA-2026:36846
- access.redhat.com/errata/RHSA-2026:50538
- access.redhat.com/errata/RHSA-2026:50572
- access.redhat.com/errata/RHSA-2026:55930
- access.redhat.com/errata/RHSA-2026:55992
- access.redhat.com/security/cve/CVE-2026-49975
Other vulnerabilities in Apache HTTP Server
- 8.1 High severity
- 8.8 High severity
- 7.3 High severity
- 8.1 High severity
- 7.5 High severity
- 7.5 High severity
Recent Memory Allocation with Excessive Size Value vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.4 High severity
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