CVE-2026-48691
📛 CVE Title
CVE-2026-48691
Description
FastNetMon Community Edition through 1.2.9 contains an integer overflow in the BGP AS_PATH attribute encoder. In src/bgp_protocol.hpp, the IPv4UnicastAnnounce::get_attributes() function computes attribute_length as 'sizeof(bgp_as_path_segment_element_t) + this->as_path_asns.size() * sizeof(uint32_t)' and stores it in a uint8_t field (line 600-605). Since uint8_t can only hold values 0-255, an AS_PATH containing more than 63 ASNs (2 + 64*4 = 258 > 255) causes silent truncation. The truncated length is used for buffer sizing, while the actual data written is the full untruncated amount, resulting in a heap buffer overflow. Similarly, the path_segment_length field at line 621 is also uint8_t, truncating with more than 255 ASNs.
Overview
- State
- PUBLISHED
- Assigner (CNA)
- mitre
- CVSS severity
- critical
- CVSS score
- 9.8 / 10
- CVSS vector
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H- Effective score
- 9.8 / 10 CRITICAL source: CNA overview
- CWE(s)
- —
- Reserved
- 2026-05-22
- Published
- 2026-05-26 00:00 UTC
- Last updated
- 2026-05-27 20:37 UTC
- Source
- https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/48xxx/CVE-2026-48691.json
- Linked Threat
- CVE-2026-48691 — CVE-2026-48691
NVD triage scoring NVD CVE 2.0
Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.
- NVD published
- 2026-05-26 17:16:53 UTC
- NVD last modified
- 2026-06-17 10:55:11 UTC
- NVD CVSS v3.1
- 9.8 / 10 CRITICAL source: nvd@nist.gov
- NVD CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H- Exploitability subscore
- 3.9 / 10
- Impact subscore
- 5.9 / 10
- EPSS score
- 0.0031 (probability of exploitation in next 30 days)
- EPSS percentile
- 22.60% vs all CVEs — higher = more likely to be exploited, as of 2026-07-08
NVD-assigned CWE(s):
CWE-190,
CWE-122
(differs from the CNA list above)
NVD / KEV / EPSS data refreshed 2026-07-08 14:43 UTC. Re-run the 🛰 Backfill from NVD button above to refresh.
European Union Vulnerability Database ENISA EUVD
ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.
- EUVD ID
-
EUVD-2026-31898 - Assigner
- mitre
- Published
- May 26, 2026, 12:00:00 AM
- Updated
- May 27, 2026, 8:37:43 PM
- EUVD base score (CVSS 3.1)
-
7.3 / 10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L - EUVD-reported EPSS
- 0.3100
- Vendors
- n/a
- Products
-
n/a (n/a)
- Aliases
-
GHSA-pjmc-gjwh-qr2w
ENISA description: FastNetMon Community Edition through 1.2.9 contains an integer overflow in the BGP AS_PATH attribute encoder. In src/bgp_protocol.hpp, the IPv4UnicastAnnounce::get_attributes() function computes attribute_length as 'sizeof(bgp_as_path_segment_element_t) + this->as_path_asns.size() * sizeof(uint32_t)' and stores it in a uint8_t field (line 600-605). Since uint8_t can only hold values 0-255, an AS_PATH containing more than 63 ASNs (2 + 64*4 = 258 > 255) causes silent truncation. The truncated length is used for buffer sizing, while the actual data written is the full untruncated amount, resulting in a heap buffer overflow. Similarly, the path_segment_length field at line 621 is also uint8_t, truncating with more than 255 ASNs.
Affected products (1)
| Vendor | Product | Versions | Platforms |
|---|---|---|---|
| n/a | n/a |
n/a (affected)
|
— |
Affected products — CPE 2.3 (1) NVD
NVD's normalized CPE 2.3 matchers, used by vendor tools (vulnerability scanners, asset managers) for automated detection. Compare with the CNA's free-text "Affected products" section above.
cpe:2.3:a:pavel-odintsov:fastnetmon:*:*:*:*:community:*:*:*
Vendor references (3)
References embedded in the original CVE record by the assigning CNA.
Web references (6)
DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.
- https://github.com/pavel-odintsov/fastnetmon tenable:github.com
- https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.hpp tenable:github.com
- https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48691-bgp-as-path-overflow tenable:lorikeetsecurity.com
- https://nvd.nist.gov/vuln/detail/CVE-2026-48691 tenable:nvd.nist.gov
- https://www.cve.org/CVERecord?id=CVE-2026-48691 tenable:www.cve.org
- https://www.first.org/epss/ tenable:www.first.org
NVD-tagged references (3)
Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.
- https://github.com/pavel-odintsov/fastnetmon cve@mitre.org Product
- https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.hpp cve@mitre.org Product
- https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48691-bgp-as-path-overflow cve@mitre.org Third Party Advisory
Remediations (19)
Remediations are stored against the linked Threat row; the list below is deduplicated across both pages.
-
web:blog.gridinsoft.com
CVE - 2026 -41089 in Windows Netlogon is now reported as actively exploited. Patch domain controllers and check LSASS, Netlogon, and authentication logs.
2026-06-04 00:10 UTC -
web:cyberpress.org
The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added two actively exploited Microsoft Defender vulnerabilities to its Known Exploited Vulnerabilities (KEV) catalog, issuing an urgent remediation directive for federal agencies with a due date of June 3, 2026 .
2026-06-04 00:10 UTC -
web:github.com
CVE ID: CVE - 2026 -41091 Vulnerability Type: Improper Link Resolution Before File Access (CWE-59 - Link Following) Affected Component: Microsoft Malware Protection Engine Root Cause: Defender fails to properly resolve links/junctions during cloud-tagged file remediation /rollback, allowing redirection of privileged writes. Impact: Local authenticated attacker can escalate from standard user to ...
2026-06-04 00:10 UTC -
web:msrc.microsoft.com
The Microsoft Security Response Center (MSRC) investigates all reports of security vulnerabilities affecting Microsoft products and services, and provides the information here as part of the ongoing effort to help you manage security risks and help keep your systems protected.
2026-06-04 00:10 UTC -
web:op-c.net
CISA added two actively exploited Microsoft Defender vulnerabilities, CVE - 2026 -41091 and CVE - 2026 -45498, to its KEV catalog. Learn the risks and recommended actions.
2026-06-04 00:10 UTC -
web:thecyberexpress.com
Microsoft confirms active exploitation of CVE - 2026 -41091 and CVE - 2026 -45498 in Defender, with CVSS-rated risks, KEV listing, and urgent patches issued.
2026-06-04 00:10 UTC -
web:thehackernews.com
Microsoft has disclosed that a privilege escalation and a denial-of-service flaw in Defender has come under active exploitation in the wild. The former, tracked as CVE - 2026 -41091, is rated 7.8 on the CVSS scoring system. Successful exploitation of the flaw could allow an attacker to gain SYSTEM ...
2026-06-04 00:10 UTC -
web:www.helpnetsecurity.com
Attackers are actively exploiting two Microsoft Defender vulnerabilities ( CVE - 2026 -41091 and CVE - 2026 -45498), Microsoft acknowledged.
2026-06-04 00:10 UTC -
web:www.malwarebytes.com
The KEV catalog tracks vulnerabilities known to be exploited in the wild and sets patch deadlines for Federal Civilian Executive Branch (FCEB) agencies. Five of the added vulnerabilities are quite old by vulnerability standards. Patches were released in 2008, 2009, and 2010. But the Microsoft Defender vulnerabilities are from this year. Those ...
2026-06-04 00:10 UTC -
web:www.securityweek.com
Microsoft this week released patches for two vulnerabilities in Defender, warning they have been exploited in the wild as zero-days. The first, tracked as CVE - 2026 -41091 (CVSS score of 7.8), is described as a link-following issue that allows attackers to elevate their privileges to System. "Improper link resolution before file access ('link following') in Microsoft Defender allows an ...
2026-06-04 00:10 UTC -
web:blog.qualys.com
May 2026's Patch Tuesday arrives with Microsoft addressing a fresh set of vulnerabilities across its ecosystem, reinforcing the ongoing need for timely patching in an increasingly threat-heavy…
2026-06-19 02:26 UTC -
web:msrc.microsoft.com
Security Update Guide - Microsoft Security Response Center
2026-06-19 02:26 UTC -
web:nvd.nist.gov
Description An authorization issue was addressed with improved state management. This issue is fixed in Safari 26.4, iOS 26.4 and iPadOS 26.4, macOS Tahoe 26.4, visionOS 26.4, watchOS 26.4. A maliciously crafted webpage may be able to fingerprint the user.
2026-06-19 02:26 UTC -
web:www.action1.com
Patch Tuesday is a scheduled release day for software patches, primarily used by Microsoft, to fix security vulnerabilities, bugs, and performance issues in its software products like Windows, Office, and Azure. It occurs monthly and aims to standardize the process of delivering security updates to ensure devices remain protected.
2026-06-19 02:26 UTC -
web:www.malwarebytes.com
Microsoft says it's working on a fix for an unpatched Defender vulnerability that can give attackers the highest level of access on Windows.
2026-06-19 02:26 UTC -
web:www.msn.com
Every federal civilian agency running Microsoft Defender now faces a two-week countdown to fix two actively exploited security flaws. CISA added CVE - 2026 -41091 and CVE - 2026 -45498 to its Known ...
2026-06-19 02:26 UTC -
web:www.rapid7.com
Microsoft is publishing 200 vulnerabilities on June 2026 Patch Tuesday, including an HTTP/2 denial of service vulnerability and an elevation of privilege vulnerability in PowerToys.
2026-06-19 02:26 UTC -
web:www.veeam.com
When a vulnerability is identified, our team promptly develops a patch to address and mitigate the risk. In line with our dedication to transparency, we publicly disclose the vulnerability and provide detailed mitigation information.
2026-06-19 02:26 UTC -
web:zecurit.com
Get the complete breakdown of Microsoft's June 2026 Patch Tuesday. We analyze the latest security updates and all critical CVEs .
2026-06-19 02:26 UTC
AI Forensic Analysis
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Raw JSON
The full cvelistV5 record. Download as CVE-2026-48691.json.
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"confidentialityImpact": "LOW",
"integrityImpact": "LOW",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
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