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Weakness · VariantCWE-121

CWE-121: Stack-based Buffer Overflow

Likelihood of exploit: HighKEV-linkedVariant

As of 2026-10-05, CWE-121 (Stack-based Buffer Overflow) underlies 28 CVEs tracked by Threadlinqs, 3 of them in the CISA Known Exploited Vulnerabilities catalog, and is cited by 39 tracked threats. MITRE rates its likelihood of exploit as High.

CVEs
28Mapped to CWE-121
CISA KEV
3Exploited in the wild
Critical
14CVSS v3 critical CVEs
Threats
39Tracked campaigns citing it
Likelihood
HighMITRE likelihood of exploit

Last updated:

What is CWE-121?

A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

CWE-121 is a variant-level weakness in MITRE’s Common Weakness Enumeration, with a MITRE likelihood of exploit of High. Applicable platforms: Language: Memory-Unsafe; Language: C; Language: C++; Technology: Not Technology-Specific.

Source: MITRE CWE (CWE-121 definition, reproduced verbatim). Counts and linkage below are Threadlinqs data.

Consequences

  • Availability — Modify Memory, DoS: Crash, Exit, or Restart, DoS: Resource Consumption (CPU), DoS: Resource Consumption (Memory). Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.
  • Integrity, Confidentiality, Availability, Access Control — Modify Memory, Execute Unauthorized Code or Commands, Bypass Protection Mechanism. Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy.
  • Integrity, Confidentiality, Availability, Access Control, Other — Modify Memory, Execute Unauthorized Code or Commands, Bypass Protection Mechanism, Other. When the consequence is arbitrary code execution, this can often be used to subvert any other security service.

Source: MITRE CWE, common consequences.

How CWE-121 is exploited in the wild

Threadlinqs maps 28 CVEs to CWE-121, published between 2025-01-08 and 2026-09-29. 3 are listed in CISA’s Known Exploited Vulnerabilities catalog, the authoritative record of exploitation in the wild, and 1 is tied to ransomware campaigns. By CVSS v3 severity the set splits into 14 critical, 8 high, 3 medium, 1 low. The highest EPSS score in the set is 94.1% (CVE-2025-0282), the modelled probability of exploitation in the next 30 days. 39 tracked threats reference CWE-121 directly or through a CVE it covers; the most recent is “Fortra Patches Critical Vulnerabilities in BoKS Privileged Access Manager (CVE-2026-79901, CVE-2026-79898, CVE-2026-12627)” (2026-10-03). Affected products concentrate in QNAP Systems Inc. (5), D-Link (2), Microsoft (2), among 19 vendors in total.

Vulnerabilities (CVEs)

All 28 CVEs mapped to CWE-121, CISA KEV first, then by CVSS score.

  • CVE-2025-53521 — CISA KEV · CVSS 9.8 critical · EPSS 41.4% · published 2025-10-15
  • CVE-2025-0282 — CISA KEV · CVSS 9 critical · EPSS 94.1% · published 2025-01-08
  • CVE-2026-7273 — CISA KEV · CVSS 8.8 high · EPSS 0.3% · published 2026-06-16
  • CVE-2026-94089 — CVSS 10 critical · EPSS 0.9% · published 2026-09-20
  • CVE-2026-79911 — CVSS 10 critical · EPSS 0.6% · published 2026-08-25
  • CVE-2026-82592 — CVSS 9.9 critical · EPSS 0.7% · published 2026-08-30
  • CVE-2026-19959 — CVSS 9.9 critical · EPSS 0.4% · published 2026-08-16
  • CVE-2026-51807 — CVSS 9.8 critical · EPSS 0.2% · published 2026-07-14
  • CVE-2026-41089 — CVSS 9.8 critical · EPSS 0.1% · published 2026-05-12
  • CVE-2026-90558 — CVSS 9.8 critical · published 2026-09-12
  • CVE-2026-91843 — CVSS 9.8 critical · published 2026-09-16
  • CVE-2026-33826 — CVSS 9.1 critical · EPSS 1.0% · published 2026-04-14
  • CVE-2026-26240 — CVSS 9.1 critical · EPSS 0.3% · published 2026-06-10
  • CVE-2026-26241 — CVSS 9.1 critical · EPSS 0.3% · published 2026-06-10
  • CVE-2025-68670 — CVSS 9.1 critical · EPSS 0.2% · published 2026-01-27
  • CVE-2026-4747 — CVSS 8.8 high · EPSS 1.9% · published 2026-03-26
  • CVE-2026-26239 — CVSS 8.1 high · EPSS 0.2% · published 2026-06-10
  • CVE-2026-86093 — CVSS 7.5 high · EPSS 0.4% · published 2026-09-10
  • CVE-2026-88388 — CVSS 7.5 high · EPSS 0.3% · published 2026-09-24
  • CVE-2026-67866 — CVSS 7.5 high · EPSS 0.2% · published 2026-08-05
  • CVE-2023-20577 — CVSS 7.4 high · EPSS 0.1% · published 2026-09-02
  • CVE-2025-66280 — CVSS 7.2 high · EPSS 0.3% · published 2026-06-10
  • CVE-2025-62858 — CVSS 6.5 medium · EPSS 0.3% · published 2026-06-09
  • CVE-2026-68516 — CVSS 6.5 medium · published 2026-08-24
  • CVE-2026-96676 — CVSS 6.3 medium · EPSS 0.2% · published 2026-09-23
  • CVE-2026-21807 — CVSS 3.9 low · EPSS 0.0% · published 2026-08-26
  • CVE-2026-18145 — EPSS 0.3% · published 2026-09-29
  • CVE-2026-7260 — EPSS 0.1% · published 2026-07-30

Affected vendors

  • QNAP Systems Inc. — 5 CVEs
  • D-Link — 2 CVEs
  • Microsoft — 2 CVEs
  • AMD — 1 CVE
  • AcademySoftwareFoundation — 1 CVE
  • Edimax — 1 CVE
  • F5 — 1 CVE
  • Fast — 1 CVE
  • FreeBSD — 1 CVE
  • HCLSoftware — 1 CVE
  • IBM — 1 CVE
  • Ivanti — 1 CVE

Threat activity

39 tracked threats cite CWE-121; the 25 most recent are listed.

Mitigations

  • Operation, Build and Compilation / Environment Hardening: 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 [REF-1334] discusses canary-based detection in detail.
  • Architecture and Design: Use an abstraction library to abstract away risky APIs. Not a complete solution.
  • Implementation: Implement and perform bounds checking on input.
  • Implementation: Do not use dangerous functions such as gets. Use safer, equivalent functions which check for boundary errors.
  • Operation, Build and Compilation / Environment Hardening: Run or compile the software using features or extensions that randomly arrange the positions of a program's executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code. Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as "rebasing" (for Windows) and "prelinking" (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would…

Source: MITRE CWE, potential mitigations.

Detection methods (MITRE CWE)

  • Fuzzing (effectiveness: High): Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.
  • Automated Static Analysis (effectiveness: High): Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
  • Automated Dynamic Analysis (effectiveness: Moderate): Use tools that are integrated during compilation to insert runtime error-checking mechanisms related to memory safety errors, such as AddressSanitizer (ASan) for C/C++ [REF-1518].

Source: MITRE CWE, detection methods. Threadlinqs detection rules for the threats above are Blue tier and higher.