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CVE-2026-8674— Assertion failure in the DNS stub resolver with a long search domain

Quick assessment

Affected
The GNU C Library glibc
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.

在 GNU C Library（glibc）2.26 到 2.44 版本中，当从 文件或 环境变量初始化 DNS 桩解析器（stub resolver）时，如果其搜索列表中包含一个长度约为 200 个字符或更长的域名，会导致断言失败，从而使进程中止（abort）。 具体机制如下：解析器在将搜索列表复制到固定大小的 缓冲区时会对其进行截断，随后会执行一个断言，以校验该副本是否与完整配置保持一致。然而，该一致性检查使用了错误的大小进行比较，且未能正确处理第一个条目无法完整放入缓冲区的场景，导致正确截断后的列表在断言时失

CVSS 5.3 · Medium

Affected Version Matrix 1

VendorProduct Version RangeStatus
The GNU C Library glibc 2.26≤ 2.44 affected
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I. Basic Information for CVE-2026-8674

Vulnerability Information
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Vulnerability Title
Assertion failure in the DNS stub resolver with a long search domain
Source: CVE Program / CVE List V5
Vulnerability Description
Initializing the DNS stub resolver from an /etc/resolv.conf file, or a LOCALDOMAIN environment variable, whose search list contains a domain of roughly 200 characters or more in the GNU C Library version 2.26 to 2.44 results in an assertion failure which aborts the process. The resolver truncates the search list when copying it into the fixed-size _res.defdname buffer, then asserts that the copy is consistent with the full configuration. The consistency check compared against the wrong size and did not handle a first entry that does not fit, so a correctly truncated list failed the assertion. Any process that resolves names through the library is affected, including long-running processes that reload /etc/resolv.conf on the next query after it changes. Search domains are commonly written to /etc/resolv.conf from data received over DHCP or from a VPN server, so an attacker on the local network may be able to trigger this without privileges on the target system, subject to validation by the network configuration software.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
可达断言
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
The GNU C Library glibc 2.26 ~ 2.44 -

II. Public POCs for CVE-2026-8674

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III. Intelligence Information for CVE-2026-8674

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Patches & Fixes for CVE-2026-8674 (1)

Vendor Advisories for CVE-2026-8674 (1)

Security Blog Posts for CVE-2026-8674 (1)

Other References for CVE-2026-8674 (1)

IV. Related Vulnerabilities

Same product: glibc
Same vendor: The GNU C Library
Same weakness: CWE-617

V. Comments for CVE-2026-8674

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