CVE-2026-27820— zlib: Buffer Overflow in Zlib::GzipReader ungetc via large input leads to memory corruption
Quick assessment
Affected
ruby zlib
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
zlib是美国Mark Adler个人开发者的一个通用的数据压缩库。 zlib 3.0.0及以下版本、3.1.0版本、3.1.1版本、3.2.0版本和3.2.1版本存在安全漏洞，该漏洞源于Zlib::GzipReader存在缓冲区溢出，可能导致内存损坏。
Possible ATT&CK Techniques 1 AI
T1203 · Exploitation for Client Execution
Get alerts for future matching vulnerabilities
Log in to subscribe
I. Basic Information for CVE-2026-27820
Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗
Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.
Vulnerability Title
zlib: Buffer Overflow in Zlib::GzipReader ungetc via large input leads to memory corruption
Source: CVE Program / CVE List V5
Vulnerability Description
zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U
Source: CVE Program / CVE List V5
Vulnerability Type
未进行输入大小检查的缓冲区拷贝(传统缓冲区溢出)
Source: CVE Program / CVE List V5
Vulnerability Title
zlib 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
zlib是美国Mark Adler个人开发者的一个通用的数据压缩库。 zlib 3.0.0及以下版本、3.1.0版本、3.1.1版本、3.2.0版本和3.2.1版本存在安全漏洞，该漏洞源于Zlib::GzipReader存在缓冲区溢出，可能导致内存损坏。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
II. Public POCs for CVE-2026-27820
| # | POC Description | Source Link | Shenlong Link |
|---|
AI-Generated POC
Premium
No public POC found.
Login to generate AI POCIII. Intelligence Information for CVE-2026-27820
请登录查看更多情报信息。
IV. Related Vulnerabilities
Same product: zlib
-
CVE-2026-85091
zlib 1.3.1.2 through 1.3.2 Heap Buffer Overflow via gz_vacat -
CVE-2026-76844
zlib 1.2.11 through 1.3.2 Heap Buffer Overflow via Stale gzw -
CVE-2026-27171
zlib 安全漏洞 -
CVE-2026-22184
zlib <= 1.3.1.2 untgz Global Buffer Overflow in TGZfname() -
CVE-2023-6992
Memory corruption issues is Cloudflare zlib implementation
Same vendor: ruby
Same weakness: CWE-120
-
CVE-2026-103227
GPAC DASH Client dash_client.c gf_dash_resolve_url buffer ov -
CVE-2026-81433
Fireware OS Pre-Authentication Stack Buffer Overflow in fing -
CVE-2026-102296
ZoneMinder before 1.38.4 Buffer Overflow via HTTP Camera Res -
CVE-2026-6730
Multiple Vulnerabilities in IBM Concert Software -
CVE-2026-94101
Netcore NBR200V2 routerd vlan_load_form_uci buffer overflow
V. Comments for CVE-2026-27820
No comments yet