Proxy denial of service via cached header growth
Published Nov 3, 2023 · Updated Nov 6, 2025
Denial of service in Squid on Red Hat Enterprise Linux allows remote attackers to stall or crash proxy workers through cached headers. Squid validates each received response header before caching, but repeated HTTP 304 updates can grow the cached header beyond the configured limit; parsing that oversized header from disk then stalls or crashes a worker. Disk caching must be enabled and the attacker must cause Squid to cache and later reuse the crafted response, after which all clients using that worker lose proxy service.
Summary
What happened
Denial of service in Squid on Red Hat Enterprise Linux allows remote attackers to stall or crash proxy workers through cached headers. Squid validates each received response header before caching, but repeated HTTP 304 updates can grow the cached header beyond the configured limit; parsing that oversized header from disk then stalls or crashes a worker. Disk caching must be enabled and the attacker must cause Squid to cache and later reuse the crafted response, after which all clients using that worker lose proxy service.
The record
- CVE
- CVE-2023-5824
- Published
- Nov 3, 2023
- Updated
- Nov 6, 2025
- Vendor
- Red Hat
- Product
- Red Hat Enterprise Linux 6
- Classifications
- CWE-791, CWE-400, CWE-237, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Nov 3, 2023CVE publishedPublication date reported by the CVE source.
- Nov 6, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.
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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