CVE-2026-75649

Executive Summary

CVE-2026-75649 is a heap-based buffer overflow (CWE-122) affecting an application or component identified only as "Bridge," for which no vendor attribution, version range, or patch information has been published in the available intelligence feeds. Successful exploitation requires user interaction — specifically, a victim must open a malicious file — and yields arbitrary code execution in the security context of the current user. With a CVSS v3.1 base score of 7.8 (High) and no public proof-of-concept, no Nuclei template, no known exploit code, and no CISA KEV listing, this vulnerability currently presents a latent but significant risk: file-format attack surface, high confidentiality/integrity/availability impact upon success, and zero available remediation from an authoritative source.

Technical Analysis

CVE-2026-75649 is classified under CWE-122: Heap-based Buffer Overflow. This vulnerability class occurs when a program writes more data to a heap-allocated buffer than the buffer was sized to hold, corrupting adjacent heap metadata and neighboring allocations. Unlike stack-based overflows, heap overflows do not typically overwrite a return address directly; instead, exploitation generally proceeds by corrupting heap chunk headers, function pointers stored in adjacent allocations, or by manipulating allocator metadata to achieve an arbitrary write primitive during subsequent allocation or free operations. Modern allocators (glibc malloc, Windows NT heap, jemalloc) include hardening that raises the exploitation bar, but the class remains reliably weaponizable when the attacker can control overflow length and placement of adjacent objects.

The critical operational characteristics of this finding, as stated in the NVD description, are:

• Attack vector is local (AV:L). The vulnerability is not remotely reachable over a network service. Exploitation is delivered through a file or local interaction path.
• No privileges required (PR:N). The attacker does not need any prior authentication or elevated privilege on the target system.
• User interaction is required (UI:R). A victim must actively open a malicious file. This is the classic client-side, file-parser attack model: the victim is the delivery mechanism, and the vulnerable code executes with that victim's privileges.
• Impact scope is unchanged (S:U). Successful exploitation does not cross a security boundary within the CVSS model — code runs as the current user.
• Confidentiality, Integrity, and Availability impacts are all High (C:H/I:H/A:H). Full compromise of data accessible to the user, ability to modify data, and ability to disrupt availability (e.g., via crash or resource exhaustion) are all anticipated on successful exploitation.

Attack surface. The vulnerable surface is the file-parsing or file-loading path of the "Bridge" component. Because the flaw is reachable by opening a crafted file, the input is untrusted, attacker-supplied file content. The precise parsing routine, the specific file format, and the exact field that overflows are not disclosed in the available NVD description or CNA title, so no function names, offsets, magic bytes, or structure fields are asserted here. Any claim about the specific parsing function, the malformed field, or the exact byte pattern required would be speculation and is deliberately omitted.

Root cause class. At a class level, the defect is an unchecked or improperly validated length/count value in file input being used to size or bound a heap allocation. When a crafted file supplies a size or length field that the parser trusts without validation against the actual buffer, a subsequent copy operation writes past the allocation boundary. This is a textbook CWE-122 pattern.

Exploitability state. There is currently no public exploit code, no Nuclei template, and no public proof-of-concept associated with this CVE in the provided data. EPSS has not been scored by FIRST.org, so no probability-of-exploitation estimate is available; that absence must not be read as a low-likelihood signal — it simply means the model has insufficient data. The patch confidence is 0/4, meaning no tracked source (vendor advisory, OSV, distro tracker, or NVD patch reference) evidences a fix.

Exploitation Scenarios

No public PoC exists for CVE-2026-75649. The attack chain below is therefore described at the vulnerability-class level, consistent with CWE-122 and the NVD description, and does not assert specific function names, file formats, or byte layouts.

1) Reconnaissance / target identification. An adversary identifies environments where the "Bridge" component is installed and where users routinely open externally supplied files (email attachments, shared documents, downloaded project files, chat-delivered documents). Because no vendor attribution or version range is available, precise fingerprinting from the data provided is not possible; targeting would rely on identifying installations of the affected product through endpoint software inventory, file-association registry entries, or application presence on user workstations. Shodan/FOFA-style external reconnaissance is of limited value here because the vector is local and file-driven rather than network-listening — the vulnerable process is reached through a file open, not an open socket.

2) Trigger of the specific flaw class. The attacker crafts a malicious file containing a length, count, or size field that is not validated against the destination buffer's actual size. When the victim opens the file, the vulnerable "Bridge" parser reads the attacker-controlled value and performs a copy/write operation sized by that value into a heap allocation that is smaller than the value advertises. This overflows the heap chunk. No specific format, field name, or parser routine can be named from the available description.

3) Execution method (vulnerability-class level). Heap corruption alone is not code execution. The attacker's payload strategy operates at the class level: place controlled data adjacent to the overflowed allocation so that the overwrite corrupts an object of security interest — a function pointer, vtable pointer, or allocator metadata — and arrange for that corrupted value to be dereferenced or acted upon after the overflow. Because CVSS indicates PR:N and S:U, the resulting code executes with the current user's privileges: no privilege escalation occurs within this CVE, but any rights the user holds (file access, credentials cached in-session, ability to run user-scope scripts) are inherited by the attacker's code.

4) Post-exploitation impact. Per the CVSS subscores (C:H/I:H/A:H), post-exploitation impact includes: reading any file the user can read (documents, source code, cached credentials, browser data), modifying user-accessible data (integrity of documents, configuration, potentially user-scope startup items), and disrupting availability (crashes or resource exhaustion). If the user runs with administrative privileges — common in many workstation configurations — the attacker's code likewise runs with those privileges, materially broadening blast radius, though that escalation is a property of the user's context, not of the vulnerability itself.

It must be reiterated: no specific exploitation steps, malformed-field constructions, or offsets are derivable from the source data. Treat the above as the shape of the attack, not a recipe.

Impact Assessment

Business impact. Successful exploitation delivers arbitrary code execution in the user's context, enabling espionage (data theft), sabotage (document destruction, ransomware staging at user scope), and lateral movement from the compromised endpoint via the user's credentials. Because delivery is a file-open, the natural ingress is email and collaboration platforms — the highest-volume malware delivery channels in enterprise environments.

Affected systems. The affected product is identified only as "Bridge." No vendor, version range, OSV package list, or affected-version data was provided. As a result, the full population of affected systems cannot be enumerated from available intelligence. Asset owners must self-identify whether any software named "Bridge" in their estate matches the CNA description and treat those installations as potentially vulnerable until a vendor advisory clarifies scope.

Blast radius and CVSS reference.

• Base 7.8 (High) — AV:L (local/file-driven), AC:L (no special conditions beyond the file), PR:N (no prior auth), UI:R (victim must open the file), S:U (no boundary crossing in the model), C:H/I:H/A:H (total loss of CIA within the user's scope).
• The UI:R requirement is the primary mitigating factor in the score and the primary control point in practice: user awareness and email/attachment controls directly reduce exposure.
• The AV:L + UI:R combination places this firmly in the client-side file-parser risk family — a class historically favored by targeted phishing and "malicious document" campaigns because it needs no network-reachable service.

Exploitation likelihood. EPSS not scored, no public exploit, no KEV listing. Current real-world exploitation evidence is absent from the provided feeds. However, CWE-122 file-parser bugs are commonly weaponized once technical details emerge, so absence of public exploit today should not lower vigilance.

Detection Guidance

Detection for this CVE is challenging because the specific file format and parser behavior are undisclosed. The following rules therefore focus on behavioral post-exploitation signals (unexpected child processes, memory corruption crashes, suspicious file-open-then-execute chains) and on generic heap-overflow indicators. These are engineering templates to be tuned to the actual product once a vendor advisory is available.

Sigma Rule

title: Potential Heap Buffer Overflow Exploitation - Bridge Component Child Process
id: 3f9c2a10-7564-4cve-8b21-000000000049
status: experimental
description: Detects a file-handler "Bridge" process spawning unusual child processes or interpreters, consistent with client-side RCE following CVE-2026-75649 (heap-based buffer overflow, user opens malicious file).
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-75649
author: Valters IT Threat Intel
date: 2026/01/01
logsource:
  category: process_creation
  product: windows
detection:
  selection_parent:
    ParentImage|endswith:
      - '\bridge.exe'
      - '\bridge'
  selection_child_suspicious:
    Image|endswith:
      - '\cmd.exe'
      - '\powershell.exe'
      - '\wscript.exe'
      - '\cscript.exe'
      - '\mshta.exe'
      - '\rundll32.exe'
      - '\regsvr32.exe'
  filter_maintenance:
    CommandLine|contains:
      - '--version'
      - '/help'
  condition: selection_parent and selection_child_suspicious and not filter_maintenance
falsepositives:
  - Legitimate Bridge integrations that invoke scripting engines
level: high
tags:
  - attack.t1203
  - cve.2026.75649

YARA Rule

rule EXPLOIT_CVE_2026_75649_HeapOverflow_Generic
{
    meta:
        description = "Generic heuristic for heap-overflow exploitation artifacts associated with CVE-2026-75649 (Bridge, CWE-122). Detects common heap-spray / ROP staging markers in dropped payloads. Tune before production use."
        author = "Valters IT Threat Intel"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-75649"
        date = "2026-01-01"
        severity = "high"

    strings:
        $mz   = { 4D 5A }
        $heap1 = "HeapAlloc" ascii nocase
        $heap2 = "RtlAllocateHeap" ascii nocase
        $spray1 = { 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 }
        $cve   = "CVE-2026-75649" ascii nocase

    condition:
        uint16(0) == 0x5A4D and
        ( $cve or
          ( 1 of ($mz) and 16 of ($spray1) ) or
          1 of ($heap1, $heap2) )
}

Suricata IDS Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"EXPLOIT CVE-2026-75649 Possible Bridge Client-Side RCE C2 Check-in"; flow:established,to_server; content:"CVE-2026-75649"; http_user_agent; sid:202675649; rev:1; metadata:created_at 2026_01_01, cve CVE_2026_75649; classtype:attempted-admin; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-75649;)
alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"EXPLOIT CVE-2026-75649 Suspicious Document-Handler Egress Post-File-Open"; flow:established,to_server; dsize:>500; content:"|4D 5A|"; depth:2; sid:202675650; rev:1; metadata:created_at 2026_01_01, cve CVE_2026_75649; classtype:trojan-activity;)

Note: because the vulnerable path is local/file-driven with no known network signature, Suricata coverage necessarily targets post-exploitation egress and C2 staging rather than the exploit trigger itself.

Elastic Detection

process where event.type == "start" and
  process.parent.name : ("bridge", "bridge.exe") and
  process.name : ("cmd.exe", "powershell.exe", "wscript.exe", "cscript.exe",
                  "mshta.exe", "rundll32.exe", "regsvr32.exe", "curl.exe", "certutil.exe")

process where event.type == "start" and
  process.parent.name : ("bridge", "bridge.exe") and
  process.name : ("bridge", "bridge.exe") and
  process.executable : ("C:\\Users\\*", "C:\\Temp\\*", "\\AppData\\*")

Splunk SPL Query

index=sysmon (EventCode=1 OR EventCode=10)
| where (match(lower(ParentImage), "bridge(\.exe)?$") AND match(lower(Image), "(cmd|powershell|wscript|cscript|mshta|rundll32|regsvr32)\.exe$"))
| table _time, ComputerName, User, ParentImage, Image, CommandLine, CallTrace
| eval cve="CVE-2026-75649", tactic="T1203"
| sort - _time

index=sysmon EventCode=10
| where match(lower(SourceImage), "bridge(\.exe)?$")
| where GrantedAccess IN ("0x1fffff","0x1f0fff","0x1410","0x40")
| stats count values(TargetImage) as targets by ComputerName, SourceImage
| where count > 5

Wazuh OSSEC Rule

<group name="cve_2026_75649,exploit,">
  <rule id="100649" level="12">
    <if_sid>61603</if_sid>
    <field name="win.eventdata.parentImage">bridge\.exe$</field>
    <field name="win.eventdata.image">(cmd|powershell|wscript|cscript|mshta|rundll32|regsvr32)\.exe$</field>
    <description>CVE-2026-75649: Possible RCE - Bridge process spawned suspicious interpreter (heap overflow exploitation)</description>
    <mitre>
      <id>T1203</id>
    </mitre>
    <group>cve_2026_75649,</group>
  </rule>

  <rule id="100650" level="10">
    <if_sid>61603</if_sid>
    <field name="win.eventdata.parentImage">bridge\.exe$</field>
    <field name="win.eventdata.image">bridge\.exe$</field>
    <field name="win.eventdata.image">\\AppData\\|\\Temp\\|\\Users\\Public\\</field>
    <description>CVE-2026-75649: Bridge spawned a copy of itself from a user-writable path (possible exploitation staging)</description>
    <mitre>
      <id>T1203</id>
    </mitre>
    <group>cve_2026_75649,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 — UNPATCHED. No vendor advisory, OSV entry, distro tracker, or NVD patch reference evidences a fix. Workarounds: N/A (none supplied). Affected versions: none enumerated. Consequently the guidance below is compensating-control based until an authoritative fix exists.

1) Immediate mitigations (no vendor fix available):

• Treat files from untrusted sources as hostile. Enforce email gateway and endpoint policies that strip or sandbox active/macro-enabled content and unknown file types before they reach users.
• Disable or restrict file-association handling for the "Bridge" component for non-essential users where operationally feasible; remove it from the set of default handlers for untrusted file types.
• Apply least privilege to users. Because exploitation yields code execution at the user's privilege level, removing local administrator rights from standard users materially reduces potential impact.
• Application allowlisting / WDAC / AppLocker to block execution of unauthorized binaries that a heap-overflow payload might drop or invoke (interpreters, LOLBins from user-writable paths).
• Exploit protection features: enable OS-level mitigations — ASLR, CFG, DEP, and, where available, Windows Exploit Protection settings (SEHOP, Heap Integrity, Arbitrary Code Guard) on hosts running the "Bridge" component.
• Deploy the detection content above to alert on the file-open→child-process and file-open→self-spawn patterns indicative of exploitation.

2) Patch / upgrade steps:

• Monitor for a vendor advisory. No vendor is attributed in the source data; asset owners must first identify the exact product/maker behind "Bridge" in their environment and register for that vendor's security bulletins.
• Subscribe to NVD and the applicable CNA feed for CVE-2026-75649 to receive the patch reference immediately upon publication.
• Once a fixed version is released: inventory all installations, stage the update, verify the installed version matches or exceeds the fixed release, and re-scan. Until then, there is no supported apply-a-patch action.

3) Long-term hardening:

• Vulnerability-management coverage: ensure file-parser components and desktop applications are included in authenticated scanning and SBOM-based inventory, not only network-facing services — client-side file parsers are frequently under-instrumented.
• Memory-safe remediation advocacy: for the affected product vendor, push for fixes that use bounded copy primitives and input-length validation (the CWE-122 root cause), and for memory-safe language adoption or hardened allocators in the component's build.
• User-awareness training specifically on opening unsolicited attachments/documents, reinforced by technical controls rather than relying on awareness alone.
• Egress and endpoint telemetry retention sufficient to investigate client-side compromise after the fact, since the exploit trigger itself is local and largely unobservable on the wire.
• Fuzz the relevant parsers internally if the "Bridge" component is in-house or open source, to surface adjacent CWE-122 defects proactively.

References

• NVD — CVE-2026-75649: https://nvd.nist.gov/vuln/detail/CVE-2026-75649
• MITRE CWE-122 — Heap-based Buffer Overflow: https://cwe.mitre.org/data/definitions/122.html
• MITRE ATT&CK T1203 — Exploitation for Client Execution: https://attack.mitre.org/techniques/T1203/
• FIRST — CVSS v3.1 Specification (score 7.8, vector CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H): https://www.first.org/cvss/v3.1/specification-document
• CISA Known Exploited Vulnerabilities Catalog (CVE-2026-75649 NOT listed as of this report): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Exploit-in-the-wild / threat actor evidence: None available. There is no public PoC, no Nuclei template, no exploit code, no EPSS score, and no CISA KEV entry in the provided intelligence. No named threat actor campaign is associated with CVE-2026-75649 at this time.