Service crash via unsafe HTML rewrite buffer resizing
Published Jun 8, 2026 · Updated Jun 8, 2026
Heap buffer overflow in mod_proxy_html in Apache HTTP Server 2.4.67 and earlier allows remote attackers to crash the server. The dump_content and pstartElement paths manually resize and shift buffers with preserve, memmove, and memcpy while rewriting backend-supplied HTML content. Exploitation requires mod_proxy_html to process content from a malicious or compromised backend; the documented consequence is a service crash.
Summary
What happened
Heap buffer overflow in mod_proxy_html in Apache HTTP Server 2.4.67 and earlier allows remote attackers to crash the server. The dump_content and pstartElement paths manually resize and shift buffers with preserve, memmove, and memcpy while rewriting backend-supplied HTML content. Exploitation requires mod_proxy_html to process content from a malicious or compromised backend; the documented consequence is a service crash.
The record
- CVE
- CVE-2026-34355
- Published
- Jun 8, 2026
- Updated
- Jun 8, 2026
- Vendor
- The Apache Software Foundation
- Product
- Apache HTTP Server
- Classifications
- CWE-122, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 8, 2026CVE publishedPublication date reported by the CVE source.
- Jun 8, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=2.4.0 <=2.4.67
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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