CVE-2025-53521
When a BIG-IP APM access policy is configured on a virtual server, specific malicious traffic can lead to Remote Code Execution (RCE).
Critical
Known exploited
- Severity
- 9.3 / 10
- Critical · CVSS 4.0
- Exploit chance (EPSS)
- 2.30%
- Chance of exploitation in the next 30 days. Higher than 83.26% of scored vulnerabilities.
- Known exploited
- Yes
- In CISA's catalog since Mar 27, 2026
- Weakness
- CWE-121 Stack-based Buffer Overflow
- Fix
- None yet
- No fixed version published
Exploited in the wild. F5 BIG-IP Stack-Based Buffer Overflow Vulnerability (F5 BIG-IP). Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Due for U.S. federal agencies by Mar 30, 2026.
Description
When a BIG-IP APM access policy is configured on a virtual server, specific malicious traffic can lead to Remote Code Execution (RCE).
Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
How to fix
No fixed version has been published yet. Until one is, remove or replace the package, or turn off or isolate the affected feature. This page updates when a fix ships.
Severity breakdown
CVSS 4.0 9.3
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/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
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- None
- Privileges required
- None
- User interaction
- None
- Confidentiality (vulnerable system)
- High
- Integrity (vulnerable system)
- High
- Availability (vulnerable system)
- High
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
- Exploit maturity
- Not defined
- Scope
- X
CVSS 3.1 9.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Weakness
CWE-121: Stack-based Buffer Overflow
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).
How to prevent it
- Operation, Build and Compilation: 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: 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 require relocating the libraries at run-time, defeating the whole purpose of prelinking. For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].
References
Advisories
Other links
Timeline
- Published
- Added to CISA's Known Exploited Vulnerabilities catalog
- Remediation due for U.S. federal agencies
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| CVE-2021-27137 An issue was discovered in router/upnp/src/ssdp.c in DD-WRT before 45724. | High Known exploited | Same weakness, CWE-121 |
| GHSA-mmjf-rqrv-855v Microsoft Security Advisory CVE-2026-50527 – .NET Denial of Service Vulnerability | High | Same weakness, CWE-121 |
| GHSA-3v45-f3vh-wg7m Oj: Stack Buffer Overflow in Oj.dump via Large Indent | High | Same weakness, CWE-121 |
| CVE-2026-7273 A stack-based buffer overflow vulnerability in the CGI program of Zyxel GS1900-48HPv2 firmware versions through 2.90(ABTQ.1)C0 could allow a LAN-based,… | High Known exploited | Same weakness, CWE-121 |
| GHSA-ghm9-cr32-g9qj rust-openssl: rustMdCtxRef::digest_final() writes past caller buffer with no length check | High | Same weakness, CWE-121 |
| GHSA-98cp-rj9f-6v5g ImageMagick has has a stack-buffer-overflow in MNG encoder with oversized pallete | Medium | Same weakness, CWE-121 |
| GHSA-6588-8gv4-xfgh Microsoft Security Advisory CVE-2026-32203 – .NET and Visual Studio Denial of Service Vulnerability | High | Same weakness, CWE-121 |
| GHSA-8793-7xv6-82cf ImageMagick has an Out-of-bounds Write via InterpretImageFilename | Medium | Same weakness, CWE-121 |
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