CVE-2026-49943Network attack vector

Daemon crash via oversized AS_PATH mask expansion

Published Jun 2, 2026 · Updated Jun 2, 2026

Stack-based buffer overflow in CZ.NIC BIRD through 2.19.0 allows remote authenticated users to crash the routing daemon via a BGP UPDATE. In nest/a-path.c, parse_path() expands received AS_PATH segments into as_path_match()'s fixed 2,049-entry stack array without enforcing its capacity. Exploitation requires an established BGP peer, RFC 8654 Extended Messages, a path longer than 2,048 expanded ASNs, and a filter that evaluates an AS path mask; the resulting overwrite interrupts routing service.

CVSS severity6.3
Medium
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in CZ.NIC BIRD through 2.19.0 allows remote authenticated users to crash the routing daemon via a BGP UPDATE. In nest/a-path.c, parse_path() expands received AS_PATH segments into as_path_match()'s fixed 2,049-entry stack array without enforcing its capacity. Exploitation requires an established BGP peer, RFC 8654 Extended Messages, a path longer than 2,048 expanded ASNs, and a filter that evaluates an AS path mask; the resulting overwrite interrupts routing service.

The record

CVE
CVE-2026-49943
Published
Jun 2, 2026
Updated
Jun 2, 2026
Vendor
CZ.NIC
Product
BIRD
Classifications
CWE-121, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=2.19.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

CZ.NIC · BIRDversion=0 <=2.19.0

Published CVSS scores

6.3MITRECVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-121Stack-based Buffer Overflow
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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