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CVE-2026-42181— Lemmy: SSRF and internal image disclosure in post link metadata via unvalidated og:image

Quick assessment

Affected
LemmyNet lemmy
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.

Lemmy是Lemmy开源的一款用于构建社交新闻聚合器和网络论坛的自由软件。 Lemmy 0.19.18之前版本存在代码问题漏洞，该漏洞源于提取的og:image URL未受内部IP范围限制，可能导致服务端请求伪造。

CVSS 6.5 · Medium EPSS 0.35% · P28

Possible ATT&CK Techniques 1 AI

T1557 · Adversary-in-the-Middle

Affected Version Matrix 1

VendorProduct Version RangeStatus
LemmyNet lemmy < 0.19.18 affected
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I. Basic Information for CVE-2026-42181

Vulnerability Information
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Vulnerability Title
Lemmy: SSRF and internal image disclosure in post link metadata via unvalidated og:image
Source: CVE Program / CVE List V5
Vulnerability Description
Lemmy is a link aggregator and forum for the fediverse. Prior to version 0.19.18, Lemmy fetches metadata for user-supplied post URLs and, under the default StoreLinkPreviews image mode, downloads the preview image through local pict-rs. While the top-level page URL is checked against internal IP ranges, the extracted og:image URL is not subject to the same restriction. As a result, an authenticated low-privileged user can submit an attacker-controlled public page whose Open Graph image points to an internal image endpoint. Lemmy will fetch that internal image server-side and store a local thumbnail that can then be served back to users. This issue has been patched in version 0.19.18.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
服务端请求伪造(SSRF)
Source: CVE Program / CVE List V5
Vulnerability Title
Lemmy 代码问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Lemmy是Lemmy开源的一款用于构建社交新闻聚合器和网络论坛的自由软件。 Lemmy 0.19.18之前版本存在代码问题漏洞，该漏洞源于提取的og:image URL未受内部IP范围限制，可能导致服务端请求伪造。
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

Vendor Product Affected Versions CPE Subscribe
LemmyNet lemmy < 0.19.18 -

II. Public POCs for CVE-2026-42181

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III. Intelligence Information for CVE-2026-42181

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Vendor Advisories for CVE-2026-42181 (1)

Vendor Pages for CVE-2026-42181 (1)

IV. Related Vulnerabilities

Same product: lemmy
Same vendor: LemmyNet
Same weakness: CWE-918