esphome · zeroconf: Unbounded exception-dedup state retains packet buffers via traceback frame locals, enabling LAN-local memory
Affects esphomeSource GCVE Database
Not known to be exploited · CVSS 6.5 Medium : upgrade to 2026.5.0 when convenient.
Data as of 30 Oct 2026, 07:30 UTC
- Patch
- Available – fixed in 2026.5.0
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 13 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.
What to do
Upgrade esphome to 2026.5.0.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Homebrewesphomepkg:brew/esphomeOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
### Impact `DNSIncoming._log_exception_debug` and the four `QuietLogger` exception-dedup methods stored an unbounded `_seen_logs` dict keyed by `str(sys.exc_info()[1])`. The seven `IncomingDecodeError` messages raised from `_read_name` / `_decode_labels_at_offset` (RFC 6762 §18 name-decoding error paths) all embed `self.source` — the peer's ephemeral source port, varying per packet — plus byte `offset` and pointer `link`, so every attacker-influenced combination produced a fresh dedup key. The stored value was the full `sys.exc_info()` triple, whose traceback's frame locals retained `self.data` (the raw inbound packet, up to 8966 bytes per RFC 6762 §17). Each unique malformed packet therefore pinned ~9 KB until process exit. Any unauthenticated host on the local link (UDP/5353, `224.0.0.251` / `ff02::fb`) can drive memory growth at line rate; that includes a guest on the same Wi-Fi, a compromised IoT device, or a container on a shared bridge. On memory-constrained deployments (Home Assistant on Raspberry-Pi-class hardware is the canonical victim) sustained traffic trivially OOM-kills the process, and mDNS-dependent features (HomeKit, Chromecast/Matter, AirPlay, printers) degrade or fail. ### Patches Fixed in `zeroconf` 0.149.6 ([PR #1717](https://github.com/python-zeroconf/python-zeroconf/pull/1717)). Upgrade to `>= 0.149.6`. ### Workarounds There is no in-process workaround; upgrading is the fix. Otherwise, restrict mDNS (UDP/5353) to trusted Layer-2 segments via AP client isolation, guest-network separation, or host firewall rules. ### Resources - [PR #1717](https://github.com/python-zeroconf/python-zeroconf/pull/1717), fix - [Issue #1714](https://github.com/python-zeroconf/python-zeroconf/issues/1714), public tracking issue - [RFC 6762 §17](https://www.rfc-editor.org/rfc/rfc6762#section-17), [RFC 6762 §18](https://www.rfc-editor.org/rfc/rfc6762#section-18), [CWE-400](https://cwe.mitre.org/data/definitions/400.html)
References
- github.com/python-zeroconf/python-zeroconf/security/advisories/GHSA-phvx-9mgw-67r5 (opens in a new tab)
- github.com/python-zeroconf/python-zeroconf/issues/1714 (opens in a new tab)
- github.com/python-zeroconf/python-zeroconf/pull/1717 (opens in a new tab)
- github.com/python-zeroconf/python-zeroconf (opens in a new tab)