CVE-2026-76788 — Stack out-of-bounds write in the OSDP Control Panel reply parser
The OSDP Control Panel reply parser cp_decode_response() in subsys/mgmt/osdp/src/osdp_cp.c decodes replies from a Peripheral Device into a stack-allocated struct osdp_event. For the REPLY_KEYPPAD and REPLY_RAW reply types, the payload length is taken from the received frame and the only validation performed is that the declared length is self-consistent with the number of payload bytes present in the frame. Because the attacker controls both the length field and the frame length, that check imposes no bound, and the subsequent memcpy() writes into the fixed 64-byte data arrays of struct osdp_event_keypress / struct osdp_event_cardread (OSDP_EVENT_MAX_DATALEN). The sibling REPLY_FMT handler in the same switch already carried the missing > OSDP_EVENT_MAX_DATALEN bound. The defect is reached from cp_process_reply(), which reads bytes from the OSDP RS-485 channel and passes them through osdp_phy_check_packet() and osdp_phy_decode_packet() before dispatching on the reply ID. Triggering it requires CONFIG_OSDP with CONFIG_OSDP_MODE_CP and an application event callback registered (the normal Control Panel integration), plus a frame carrying a correct SOM, a valid CRC-16, and a matching 2-bit sequence number — all of which are computable or observable by anyone on the bus. No check ties the reply ID to the outstanding command, so an oversized REPLY_KEYPPAD or REPLY_RAW is accepted as the answer to a routine CMD_POLL. A malicious or compromised card reader, or anyone with access to the RS-485 wiring, can supply such a frame; CONFIG_OSDP_SC_ENABLED only helps while a secure channel is active, and a single unauthenticated frame carrying a bad MAC causes sc_deactivate(), after which plaintext replies are again accepted. With the default CONFIG_OSDP_UART_BUFFER_LENGTH of 256, roughly 180 bytes of fully attacker-chosen data can be written past the end of the stack-allocated event object, over saved registers and the return address on typical Cortex-M and RISC-V frame layouts (Zephyr does not enable stack canaries by default). The impact ranges from a hard crash of the access-control panel to potential control-flow hijack in the context of the OSDP receive thread. The fix adds an OSDP_EVENT_MAX_DATALEN bound to both handlers, capping each memcpy() at the size of its destination.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- Technical severity (high)+6
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Zephyrproject Zephyr).
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Zephyrproject | Zephyr | ≥ 3.3.0 and ≤ 4.4.2 | Vulnerable | CVE Program (cve.org) e CISA ADP |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 8.8 | CVSS 3.1 | High | 2.8 | 5.9 | vulnerabilities@zephyrproject.org via NIST National Vulnerability Database |
| 8.8 | CVSS 3.1 | High | — | — | zephyr via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: vulnerabilities@zephyrproject.org) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
Timeline
What happened to this CVE, newest first.
- 2026
- Source status changed · Published → Received
- Record published
- CVSS changed · 8.8
- Source status changed · → Published
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 19, 2026 – Oct 19, 2026
References
2 on the record
Elsewhere on this site
Related CVEs (same products)
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- Medium CVE-2026-19595 Zephyr RTIO syscall verifier validates output parameters for read instead of write access 8h
- Medium CVE-2026-76787 NULL pointer dereference in the UpdateHub FOTA client when probe metadata omits sha256sum 10h
- Medium CVE-2026-75083 Integer underflow of the radio-reported frame length causes an out-of-bounds write in the NXP KW41Z IEEE 802.15.4 driver 5d
- Medium CVE-2026-75084 Out-of-bounds write in the TI CC1200 IEEE 802.15.4 driver from an unvalidated radio-supplied packet length 5d
- Medium CVE-2026-75085 Out-of-bounds read from received-frame length underflow in the STM32WBA IEEE 802.15.4 driver 5d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No FIRST EPSS score.
- No fixed version, patch or mitigation documented.
- No CISA SSVC assessment.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-76788 is "Stack out-of-bounds write in the OSDP Control Panel reply parser", rated High. It affects Zephyr (Zephyrproject); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.8 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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