Apache HTTP Server: Heap-based Buffer Overflow
CVE-2026-34355 is a high-severity heap-based buffer overflow 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: 2.4.0 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 1.16% chance of exploitation within 30 days, higher than 68% of scored CVEs.
High severity with no evidence of exploitation so far.
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
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Apache | Apache HTTP Server | 2.4.0 through 2.4.67 | Not stated |
| Red Hat | JBoss Core Services for RHEL 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 10 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 10.0 Extended Update Support | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 9 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 9.6 Extended Update Support | Not specified in the record | Not stated |
| Red Hat | Red Hat JBoss Core Services 2.4.62.SP5 | Not specified in the record | Not stated |
| Red Hat | Red Hat Hardened Images | Not specified in the record | Not stated |
| Red Hat | Red Hat Insights proxy 1.5 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 6 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 7 | Not specified in the record | Not stated |
| Apache | HTTP Server | 2.4.0 up to, but not including, 2.4.68 | 2.4.68 |
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
A buffer overflow in mod_proxy_html in Apache HTTP Server 2.4.67 and earlier allows an attack by an untrusted backend. Users are recommended to upgrade to version 2.4.68, which fixes this issue.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Heap-based Buffer Overflow
The product writes past the end of a buffer that was allocated on the heap.
How developers prevent this class of flaw
- Pre-design: Use a language or compiler that performs automatic bounds checking.
- Use an abstraction library to abstract away risky APIs. Not a complete solution.
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other references
- openwall.com/lists/oss-security/2026/06/08/6Mailing List
- access.redhat.com/errata/RHSA-2026:25042
- access.redhat.com/errata/RHSA-2026:34109
- access.redhat.com/errata/RHSA-2026:41906
- access.redhat.com/errata/RHSA-2026:42828
- access.redhat.com/errata/RHSA-2026:47046
- access.redhat.com/errata/RHSA-2026:53371
- access.redhat.com/errata/RHSA-2026:56868
- access.redhat.com/errata/RHSA-2026:56869
- access.redhat.com/errata/RHSA-2026:62165
- access.redhat.com/errata/RHSA-2026:66323
- access.redhat.com/errata/RHSA-2026:67152
- access.redhat.com/security/cve/CVE-2026-34355
- bugzilla.redhat.com/show_bug.cgi?id=2486414
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34355.json
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 Heap-based Buffer Overflow vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
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