Zlib
CVE-2023-6992
MEDIUM
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V2 - Validation and Business Logic Input validation, allowlisting
|
| Impact | CVSS score of 4.0 (MEDIUM). Attack characteristics: local attack vector, high complexity, no privileges required, no user interaction not required. EPSS exploitation probability: 0.02%. |
| Exploit ScenarioDerived | Successful exploitation could compromise the medium-severity affected system. |
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Alert meAnalysisAIv1 – Mar 28, 2026
Cloudflare version of zlib library was found to be vulnerable to memory corruption issues affecting the deflation algorithm implementation (deflate.c). Rated medium severity (CVSS 4.0), this vulnerability is no authentication required.
Earlier versions of this analysis (1)
Cloudflare version of zlib library was found to be vulnerable to memory corruption issues affecting the deflation algorithm implementation (deflate.c). The issues resulted from improper input validati
RemediationAI
A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.
Affects your stack
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Technical ContextAI · show details
This vulnerability is classified under CWE-20. Cloudflare version of zlib library was found to be vulnerable to memory corruption issues affecting the deflation algorithm implementation (deflate.c). The issues resulted from improper input validation and heap-based buffer overflow. A local attacker could exploit the problem during compression using a crafted malicious file potentially leading to denial of service of the software. Patches: The issue has been patched in commit 8352d10 https://github.com/cloudflare/zlib/commit/8352d108c05db1bdc5ac3bdf834dad641694c13c . The upstream repository is not affected. Affected products include: Cloudflare Zlib.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
Lifecycle Timeline
2DescriptionCVE.org
Cloudflare version of zlib library was found to be vulnerable to memory corruption issues affecting the deflation algorithm implementation (deflate.c). The issues resulted from improper input validation and heap-based buffer overflow. A local attacker could exploit the problem during compression using a crafted malicious file potentially leading to denial of service of the software. Patches: The issue has been patched in commit 8352d10 https://github.com/cloudflare/zlib/commit/8352d108c05db1bdc5ac3bdf834dad641694c13c . The upstream repository is not affected.
Executive ViewAI
Organizations using Cloudflare version of zlib library should be aware of moderate risk from CVE-2023-6992, a input validation vulnerability rated CVSS 4.0. Exploitation could compromise the security of affected deployments. A patch is available and should be applied during regular vulnerability management.
Apply vendor patch. If patching is delayed: deploy WAF rules, restrict network access, enable logging.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.
Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.
Affected Products (CPE)CVE.org
zlib through 1.2.12 has a heap-based buffer over-read or buffer overflow in inflate in inflate.c via a large gzip header
inffast.c in zlib 1.2.8 might allow context-dependent attackers to have unspecified impact by leveraging improper pointe
The crc32_big function in crc32.c in zlib 1.2.8 might allow context-dependent attackers to have unspecified impact via v
inftrees.c in zlib 1.2.8 might allow context-dependent attackers to have unspecified impact by leveraging improper point
Heap buffer overflow in zlib 1.3.1.2 through 1.3.2 allows remote attackers to corrupt memory via crafted input to applic
MiniZip in zlib through 1.3 has an integer overflow and resultant heap-based buffer overflow in zipOpenNewFileInZip4_64
The inflateMark function in inflate.c in zlib 1.2.8 might allow context-dependent attackers to have unspecified impact v
Multiple directory traversal vulnerabilities in pigz 2.3.1 allow remote attackers to write to arbitrary files via a (1)
zlib before 1.3.2 allows CPU consumption via crc32_combine64 and crc32_combine_gen64 because x2nmodp can do right shifts
Local privilege escalation in zlib 1.3.1.2 and earlier allows authenticated users to achieve arbitrary code execution th
Race condition in pigz before 2.2.5 uses permissions derived from the umask when compressing a file before setting that
Buffer overflow in the Ruby zlib gem's Zlib::GzipReader allows remote or local attackers supplying crafted gzip data to
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