simc: Heap-based Buffer Overflow
CVE-2026-47235 is a high-severity heap-based buffer overflow vulnerability in simc from Simulationcraft, with a CVSS 4.0 base score of 7.5 out of 10. It can be exploited from the same local network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. Affected simc versions: < aff85992d284ca4621e784c6b065a271b22f629d. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.15% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of simc you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Simulationcraft | simc | < aff85992d284ca4621e784c6b065a271b22f629d | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- AdjacentThe attacker must be on the same local network segment.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- Attack requirements
- PresentThe target must be in a specific state or configuration for the attack to work.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- PassiveA user only needs to do something routine, such as viewing a page.
- Confidentiality (vulnerable system)
- HighSerious loss of confidentiality on the vulnerable system.
- Integrity (vulnerable system)
- HighSerious loss of integrity on the vulnerable system.
- Availability (vulnerable system)
- HighSerious loss of availability on the vulnerable system.
- Confidentiality (other systems)
- LowLimited loss of confidentiality on systems beyond the vulnerable one.
- Integrity (other systems)
- LowLimited loss of integrity on systems beyond the vulnerable one.
- Availability (other systems)
- LowLimited loss of availability on systems beyond the vulnerable one.
Vector: CVSS:4.0/AV:A/AC:H/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. Scored by CNA (github.com).
Official description
SimulationCraft is a tool to explore combat mechanics in World of Warcraft. In builds after release-820-01 and before the identified May 7, 2026 nightly, the `bcp_api.cpp` loop over the JSON `sockets` array uses `slot_data["sockets"].Size()` without bounding `gem_idx` by `MAX_GEM_SLOTS`, which is four in `engine/sc_enums.hpp`. The destination `gem_id` and `gem_bonus_id` arrays in `engine/item/item.hpp` have only four elements. More than four socket entries therefore write beyond `gem_id` into the adjacent `gem_bonus_id` vector storage; `bonus_list` entries can also access `gem_bonus_id` out of bounds. Corrupting a vector's `_M_start` pointer causes the `item_t` destructor to free an attacker-influenced pointer during normal cleanup. The advisory reports crashes and code execution demonstrated in a testing environment. Attack inputs can arrive through a malicious `.simc` profile with a `[[equipment]]` section, a compromised addon export, or `Battle.net API` responses modified by an attacker with a privileged network position. The fix is contained in the nightly build identified as simc-1205-01-516b5d7; no containing release tag is available.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Heap-based Buffer Overflow
The product writes past the end of a buffer that was allocated on the heap.
How developers prevent this class of flaw
- Pre-design: Use a language or compiler that performs automatic bounds checking.
- Use an abstraction library to abstract away risky APIs. Not a complete solution.
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Heap-based Buffer Overflow vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.0 High severity
- 7.8 High severity
- 7.8 High severity
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