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CVE-2026-55556— Rsyslog: Heap buffer overflow in imhttp plugin Basic Authentication handling

Quick assessment

Affected
rsyslog rsyslog
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.

Rsyslog is a rocket-fast system for log processing. From 8.2110.0 until 8.2604.0, the optional imhttp module's parse_auth_header function in contrib/imhttp/imhttp.c allocates a zero-byte heap buffer with calloc(0, len) when an HTTP Basic Authorization value ex

CVSS 8.2 · High

Affected Version Matrix 1

VendorProduct Version RangeStatus
rsyslog rsyslog >= 8.2110.0, < 8.2604.0 affected
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I. Basic Information for CVE-2026-55556

Vulnerability Information

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Vulnerability Title
Rsyslog: Heap buffer overflow in imhttp plugin Basic Authentication handling
Source: CVE Program / CVE List V5
Vulnerability Description
Rsyslog is a rocket-fast system for log processing. From 8.2110.0 until 8.2604.0, the optional imhttp module's parse_auth_header function in contrib/imhttp/imhttp.c allocates a zero-byte heap buffer with calloc(0, len) when an HTTP Basic Authorization value exceeds its fixed work buffer, then passes that pointer to apr_base64_decode. An unauthenticated remote attacker can send an oversized encoded credential to an imhttp endpoint configured for Basic Authentication, causing decoded data to overwrite adjacent heap memory before credential validation. Deployments that do not install, load, and use imhttp with Basic Authentication are not affected. The demonstrated impact is a process crash that interrupts log collection, and code execution has not been demonstrated. This issue is fixed in version 8.2604.0.
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:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
堆缓冲区溢出
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
rsyslog rsyslog >= 8.2110.0, < 8.2604.0 -

II. Public POCs for CVE-2026-55556

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III. Intelligence Information for CVE-2026-55556

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Patches & Fixes for CVE-2026-55556 (1)

Vendor Pages for CVE-2026-55556 (1)

Other References for CVE-2026-55556 (1)

IV. Related Vulnerabilities

Same product: rsyslog
Same vendor: rsyslog
Same weakness: CWE-122

V. Comments for CVE-2026-55556

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