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CVE-2026-46433 lldpd CVE debrief

CVE-2026-46433 is a MEDIUM severity vulnerability in lldpd prior to version 1.0.22. The lldpd_decode() function has a heap buffer over-read issue. The function strips 802.1Q VLAN tags from received Ethernet frames by calling memmove() to shift the frame payload 4 bytes left. However, the third argument (byte count) is incorrectly calculated as s - 2 * ETHER_ADDR_LEN instead of s - 2 * ETHER_ADDR_LEN - 4. This causes a 4-byte heap buffer over-read past the malloc(h_mtu) allocation when the received frame size equals the interface MTU.

Vendor
lldpd
Product
Unknown
CVSS
MEDIUM 6.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-09
Original CVE updated
2026-06-11
Advisory published
2026-06-09
Advisory updated
2026-06-11

Who should care

Users of lldpd versions prior to 1.0.22 should update to 1.0.22 or later to mitigate this vulnerability.

Technical summary

The vulnerability exists in the lldpd_decode() function in src/daemon/lldpd.c. The function incorrectly calculates the byte count for memmove(), leading to a heap buffer over-read.

Defensive priority

MEDIUM

Recommended defensive actions

  • Update lldpd to version 1.0.22 or later.
  • See ${ref-4} for patch details.
  • See ${ref-5} for issue tracking and patch details.
  • See ${ref-6} for product release notes.
  • See ${ref-7} for vendor advisory details.

Evidence notes

CVE-2026-46433 has a CVSS score of 6.5 and is classified as MEDIUM severity.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-46433 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-46433

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-46433 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-46433

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.